diff --git a/InnerDetector/InDetG4/BCM_G4_SD/python/BCM_G4_SDConfig.py b/InnerDetector/InDetG4/BCM_G4_SD/python/BCM_G4_SDConfig.py
index ca581ae91a121233df2eab41367f5bbd8e47472d..c4e84b014481f7aedeccd591dbdbe90500efa5cf 100644
--- a/InnerDetector/InDetG4/BCM_G4_SD/python/BCM_G4_SDConfig.py
+++ b/InnerDetector/InDetG4/BCM_G4_SD/python/BCM_G4_SDConfig.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 from AthenaCommon import CfgMgr
 from G4AtlasApps.SimFlags import simFlags
@@ -10,9 +10,11 @@ def getBCMSensorSD(name="BCMSensorSD", **kwargs):
     bare_collection_name = "BCMHits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "BCMHits"
+    region = "ID"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     kwargs.setdefault("LogicalVolumeNames", ["Pixel::bcmDiamondLog"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
     return CfgMgr.BCMSensorSDTool(name, **kwargs)
diff --git a/InnerDetector/InDetG4/BCM_G4_SD/python/BCM_G4_SDToolConfig.py b/InnerDetector/InDetG4/BCM_G4_SD/python/BCM_G4_SDToolConfig.py
index 5bcf6ddf9b1ff36d94bd59c5ee1a49050b0eb613..4da290d67b23d83d80c134239b2624ae61339fd4 100644
--- a/InnerDetector/InDetG4/BCM_G4_SD/python/BCM_G4_SDToolConfig.py
+++ b/InnerDetector/InDetG4/BCM_G4_SD/python/BCM_G4_SDToolConfig.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 from AthenaConfiguration.ComponentAccumulator import ComponentAccumulator
 from AthenaConfiguration.ComponentFactory import CompFactory
@@ -12,9 +12,12 @@ def BCMSensorSDCfg(ConfigFlags, name="BCMSensorSD", **kwargs):
     bare_collection_name = "BCMHits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "BCMHits"
-    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                                              mergeable_collection_suffix,
-                                                              merger_input_property)
+    region = "ID"
+    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                    bare_collection_name,
+                                                    mergeable_collection_suffix,
+                                                    merger_input_property,
+                                                    region)
     kwargs.setdefault("LogicalVolumeNames", ["Pixel::bcmDiamondLog"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
 
diff --git a/InnerDetector/InDetG4/BLM_G4_SD/python/BLM_G4_SDConfig.py b/InnerDetector/InDetG4/BLM_G4_SD/python/BLM_G4_SDConfig.py
index f4f5488b2ab4da173e8a0f0b3955037d9e426e49..79b99735924da032f1ae26151555c343cda4b824 100644
--- a/InnerDetector/InDetG4/BLM_G4_SD/python/BLM_G4_SDConfig.py
+++ b/InnerDetector/InDetG4/BLM_G4_SD/python/BLM_G4_SDConfig.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 from AthenaCommon import CfgMgr
 from G4AtlasApps.SimFlags import simFlags
@@ -10,9 +10,11 @@ def getBLMSensorSD(name="BLMSensorSD", **kwargs):
     bare_collection_name = "BLMHits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "BLMHits"
+    region = "ID"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     kwargs.setdefault("LogicalVolumeNames", ["Pixel::blmDiamondLog"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
     return CfgMgr.BLMSensorSDTool(name, **kwargs)
diff --git a/InnerDetector/InDetG4/BLM_G4_SD/python/BLM_G4_SDToolConfig.py b/InnerDetector/InDetG4/BLM_G4_SD/python/BLM_G4_SDToolConfig.py
index f816bda346ce349c4496a5332adcba7a0914fc32..f9aa423cde5342a88f890d73ceddcd44a4cd6c36 100644
--- a/InnerDetector/InDetG4/BLM_G4_SD/python/BLM_G4_SDToolConfig.py
+++ b/InnerDetector/InDetG4/BLM_G4_SD/python/BLM_G4_SDToolConfig.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 from AthenaConfiguration.ComponentAccumulator import ComponentAccumulator
 from AthenaConfiguration.ComponentFactory import CompFactory
@@ -8,14 +8,17 @@ BLMSensorSDTool=CompFactory.BLMSensorSDTool
 
 
 def BLMSensorSDCfg(ConfigFlags, name="BLMSensorSD", **kwargs):
-    
+
     result = ComponentAccumulator()
     bare_collection_name = "BLMHits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "BLMHits"
-    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                                              mergeable_collection_suffix,
-                                                              merger_input_property)
+    region = "ID"
+    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                    bare_collection_name,
+                                                    mergeable_collection_suffix,
+                                                    merger_input_property,
+                                                    region)
     kwargs.setdefault("LogicalVolumeNames", ["Pixel::blmDiamondLog"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
 
diff --git a/InnerDetector/InDetG4/PixelG4_SD/python/PixelG4_SDConfig.py b/InnerDetector/InDetG4/PixelG4_SD/python/PixelG4_SDConfig.py
index 2348cf5c91cba77749d92c44b581be9b0489f7f7..161d2683335e946429427c6dda5edc3b0fb1ea0f 100644
--- a/InnerDetector/InDetG4/PixelG4_SD/python/PixelG4_SDConfig.py
+++ b/InnerDetector/InDetG4/PixelG4_SD/python/PixelG4_SDConfig.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 from AthenaCommon import CfgMgr
 from G4AtlasApps.SimFlags import simFlags
@@ -10,9 +10,11 @@ def getPixelSensorSD(name="PixelSensorSD", **kwargs):
     bare_collection_name = "PixelHits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "PixelHits"
+    region = "ID"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     kwargs.setdefault("LogicalVolumeNames", ["Pixel::siBLayLog","Pixel::siLog","Pixel::dbmDiamondLog"])
     #kwargs.setdefault("LogicalVolumeNames", ["Pixel::siBLayLog","Pixel::siLog"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
diff --git a/InnerDetector/InDetG4/PixelG4_SD/python/PixelG4_SDToolConfig.py b/InnerDetector/InDetG4/PixelG4_SD/python/PixelG4_SDToolConfig.py
index bfe0d3c14a5f7f4d8081a9e00f578d2ced8eb05e..6f7b6b7896155dd96b9ae7f54def567970fc177e 100644
--- a/InnerDetector/InDetG4/PixelG4_SD/python/PixelG4_SDToolConfig.py
+++ b/InnerDetector/InDetG4/PixelG4_SD/python/PixelG4_SDToolConfig.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 from AthenaConfiguration.ComponentAccumulator import ComponentAccumulator
 from AthenaConfiguration.ComponentFactory import CompFactory
@@ -13,11 +13,13 @@ def PixelSensorSDCfg(ConfigFlags, name="PixelSensorSD", **kwargs):
     bare_collection_name = "PixelHits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "PixelHits"
-    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                                              mergeable_collection_suffix,
-                                                              merger_input_property)
+    region = "ID"
+    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                    bare_collection_name,
+                                                    mergeable_collection_suffix,
+                                                    merger_input_property,
+                                                    region)
     kwargs.setdefault("LogicalVolumeNames", ["Pixel::siBLayLog","Pixel::siLog","Pixel::dbmDiamondLog"])
-    #kwargs.setdefault("LogicalVolumeNames", ["Pixel::siBLayLog","Pixel::siLog"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
 
     result.merge(acc)
diff --git a/InnerDetector/InDetG4/SCT_G4_SD/python/SCT_G4_SDConfig.py b/InnerDetector/InDetG4/SCT_G4_SD/python/SCT_G4_SDConfig.py
index 12e86c04d138a5e61e172bda4fc6591d6125f65b..1055b364626458fd88e2fc7bbc50c05841895b39 100644
--- a/InnerDetector/InDetG4/SCT_G4_SD/python/SCT_G4_SDConfig.py
+++ b/InnerDetector/InDetG4/SCT_G4_SD/python/SCT_G4_SDConfig.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 from AthenaCommon import CfgMgr
 from G4AtlasApps.SimFlags import simFlags
@@ -10,9 +10,11 @@ def getSctSensorSD(name="SctSensorSD", **kwargs):
     bare_collection_name = "SCT_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "SCTHits"
+    region = "ID"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     kwargs.setdefault("LogicalVolumeNames", ["SCT::BRLSensor","SCT::ECSensor0","SCT::ECSensor1",
                                              "SCT::ECSensor2","SCT::ECSensor3"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
diff --git a/InnerDetector/InDetG4/SCT_G4_SD/python/SCT_G4_SDToolConfig.py b/InnerDetector/InDetG4/SCT_G4_SD/python/SCT_G4_SDToolConfig.py
index d3af78ebff43ee7e34f083a19bcb6b1932e6b67e..e222d82afde4fd0924955e3cf47f126ccfafb624 100644
--- a/InnerDetector/InDetG4/SCT_G4_SD/python/SCT_G4_SDToolConfig.py
+++ b/InnerDetector/InDetG4/SCT_G4_SD/python/SCT_G4_SDToolConfig.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 from AthenaConfiguration.ComponentAccumulator import ComponentAccumulator
 from AthenaConfiguration.ComponentFactory import CompFactory
@@ -14,8 +14,12 @@ def SctSensorSDCfg(ConfigFlags, name="SctSensorSD", **kwargs):
     bare_collection_name = "SCT_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "SCTHits"
-
-    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name, mergeable_collection_suffix, merger_input_property)
+    region = "ID"
+    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                    bare_collection_name,
+                                                    mergeable_collection_suffix,
+                                                    merger_input_property,
+                                                    region)
     kwargs.setdefault("LogicalVolumeNames", ["SCT::BRLSensor","SCT::ECSensor0","SCT::ECSensor1",
                                               "SCT::ECSensor2","SCT::ECSensor3"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
@@ -41,4 +45,3 @@ def SctSensor_CTBCfg(name="SctSensor_CTB", **kwargs):
     kwargs.setdefault("LogicalVolumeNames", ["SCT::ECSensor0"])
     kwargs.setdefault("OutputCollectionNames", ["SCT_Hits"])
     return SctSensor_CTBTool(name, **kwargs)
-  
diff --git a/InnerDetector/InDetG4/TRT_G4_SD/python/TRT_G4_SDConfig.py b/InnerDetector/InDetG4/TRT_G4_SD/python/TRT_G4_SDConfig.py
index d8c4d674ba650585e29eef3982ac1217bae95255..d14cdc5417644177ca2a4002c59c2a0895ce4400 100644
--- a/InnerDetector/InDetG4/TRT_G4_SD/python/TRT_G4_SDConfig.py
+++ b/InnerDetector/InDetG4/TRT_G4_SD/python/TRT_G4_SDConfig.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2002-2018 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 from AthenaCommon import CfgMgr
 from G4AtlasApps.SimFlags import simFlags
@@ -10,9 +10,11 @@ def getTRTSensitiveDetector(name="TRTSensitiveDetector", **kwargs):
     bare_collection_name = "TRTUncompressedHits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "TRTUncompressedHits"
+    region = "ID"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     logicalVolumeNames = ["TRT::Gas","TRT::GasMA"]
     from AtlasGeoModel.CommonGMJobProperties import CommonGeometryFlags as geoFlags
     if ( geoFlags.Run() in ["RUN2", "RUN3"] ) :
diff --git a/InnerDetector/InDetG4/TRT_G4_SD/python/TRT_G4_SDToolConfig.py b/InnerDetector/InDetG4/TRT_G4_SD/python/TRT_G4_SDToolConfig.py
index 365eada3388cd23f4ed1802ade79154cf7e03020..f641e92c5225e657dca183166af9591768c23551 100644
--- a/InnerDetector/InDetG4/TRT_G4_SD/python/TRT_G4_SDToolConfig.py
+++ b/InnerDetector/InDetG4/TRT_G4_SD/python/TRT_G4_SDToolConfig.py
@@ -1,11 +1,11 @@
-# Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 from AthenaConfiguration.ComponentAccumulator import ComponentAccumulator
 from AthenaConfiguration.ComponentFactory import CompFactory
 
 from ISF_Algorithms.collection_merger_helpersNew import CollectionMergerCfg
 
-TRTSensitiveDetectorTool =CompFactory.TRTSensitiveDetectorTool 
+TRTSensitiveDetectorTool =CompFactory.TRTSensitiveDetectorTool
 
 def TRTSensitiveDetectorCfg(ConfigFlags, name="TRTSensitiveDetector", **kwargs):
 
@@ -13,9 +13,12 @@ def TRTSensitiveDetectorCfg(ConfigFlags, name="TRTSensitiveDetector", **kwargs):
     bare_collection_name = "TRTUncompressedHits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "TRTUncompressedHits"
-    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                                              mergeable_collection_suffix,
-                                                              merger_input_property)
+    region = "ID"
+    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                    bare_collection_name,
+                                                    mergeable_collection_suffix,
+                                                    merger_input_property,
+                                                    region)
     result.merge(acc)
 
     logicalVolumeNames = ["TRT::Gas","TRT::GasMA"]
diff --git a/LArCalorimeter/LArG4/LArG4SD/python/LArG4SDConfig.py b/LArCalorimeter/LArG4/LArG4SD/python/LArG4SDConfig.py
index 3a8e8aa94076239b65a4241a3690c3c6ccc35eb4..428ad2f7398ee187a15209feb4d6c9b2c9fd2a33 100644
--- a/LArCalorimeter/LArG4/LArG4SD/python/LArG4SDConfig.py
+++ b/LArCalorimeter/LArG4/LArG4SD/python/LArG4SDConfig.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 from AthenaCommon import CfgMgr
 
@@ -127,9 +127,11 @@ def getLArEMBSensitiveDetector(name="LArEMBSensitiveDetector", **kwargs):
     bare_collection_name = "LArHitEMB"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "LArEMBHits"
+    region = "CALO"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     ## Main configuration
     kwargs.setdefault("StacVolumes",["LArMgr::LAr::EMB::STAC"])
     kwargs.setdefault("PresamplerVolumes",["LArMgr::LAr::Barrel::Presampler::Module"])
@@ -144,9 +146,11 @@ def getLArEMECSensitiveDetector(name="LArEMECSensitiveDetector", **kwargs):
     bare_collection_name = "LArHitEMEC"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "LArEMECHits"
+    region = "CALO"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     from G4AtlasApps.SimFlags import simFlags
     if simFlags.SimLayout.get_Value() not in ["tb_LArH6_2002","tb_LArH6EC_2002"]:
         kwargs.setdefault("NegIWVolumes",["LArMgr::LAr::EMEC::Neg::InnerWheel"])
@@ -167,9 +171,11 @@ def getLArFCALSensitiveDetector(name="LArFCALSensitiveDetector", **kwargs):
     bare_collection_name = "LArHitFCAL"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "LArFCALHits"
+    region = "CALO"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     kwargs.setdefault("FCAL1Volumes",["LArMgr::LAr::FCAL::Module1::Gap"])
     kwargs.setdefault("FCAL2Volumes",["LArMgr::LAr::FCAL::Module2::Gap"])
     kwargs.setdefault("FCAL3Volumes",["LArMgr::LAr::FCAL::Module3::Gap"])
@@ -184,9 +190,11 @@ def getLArHECSensitiveDetector(name="LArHECSensitiveDetector", **kwargs):
     bare_collection_name = "LArHitHEC"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "LArHECHits"
+    region = "CALO"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     #kwargs.setdefault("SliceVolumes",["LAr::HEC::Module::Depth::Slice"])
     #kwargs.setdefault("LocalVolumes",["LAr::HEC::Module::Depth::Slice::Local"])
     kwargs.setdefault("WheelVolumes",["LArMgr::LAr::HEC::Module::Depth::Slice"])
diff --git a/LArCalorimeter/LArG4/LArG4SD/python/LArG4SDToolConfig.py b/LArCalorimeter/LArG4/LArG4SD/python/LArG4SDToolConfig.py
index 9a32083059e755c63f25388a296284dbd84f1931..9aa1dbdd5fc0035fc1740d03d81906e14f27e6cd 100644
--- a/LArCalorimeter/LArG4/LArG4SD/python/LArG4SDToolConfig.py
+++ b/LArCalorimeter/LArG4/LArG4SD/python/LArG4SDToolConfig.py
@@ -176,9 +176,12 @@ def LArEMBSensitiveDetectorCfg(ConfigFlags,name="LArEMBSensitiveDetector", **kwa
     bare_collection_name = "LArHitEMB"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "LArEMBHits"
-    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                                              mergeable_collection_suffix,
-                                                              merger_input_property)
+    region = "CALO"
+    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                    bare_collection_name,
+                                                    mergeable_collection_suffix,
+                                                    merger_input_property,
+                                                    region)
 
     result.merge(acc)
     ## Main configuration
@@ -195,7 +198,7 @@ def LArEMBSensitiveDetectorCfg(ConfigFlags,name="LArEMBSensitiveDetector", **kwa
 
     result.merge(EMBCalculatorCfg(ConfigFlags))
     kwargs.setdefault("EMBCalculator", result.getService("EMBCalculator"))
-    
+
     result.setPrivateTools( LArG4__EMBSDTool(name, **kwargs) )
     return result
 
@@ -204,9 +207,12 @@ def LArEMECSensitiveDetectorCfg(ConfigFlags, name="LArEMECSensitiveDetector", **
     bare_collection_name = "LArHitEMEC"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "LArEMECHits"
-    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                                              mergeable_collection_suffix,
-                                                              merger_input_property)
+    region = "CALO"
+    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                    bare_collection_name,
+                                                    mergeable_collection_suffix,
+                                                    merger_input_property,
+                                                    region)
     result.merge(acc)
 
     if ConfigFlags.GeoModel.AtlasVersion not in ["tb_LArH6_2002","tb_LArH6EC_2002"]:
@@ -254,9 +260,12 @@ def LArFCALSensitiveDetectorCfg(ConfigFlags, name="LArFCALSensitiveDetector", **
     bare_collection_name = "LArHitFCAL"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "LArFCALHits"
-    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                                              mergeable_collection_suffix,
-                                                              merger_input_property)
+    region = "CALO"
+    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                    bare_collection_name,
+                                                    mergeable_collection_suffix,
+                                                    merger_input_property,
+                                                    region)
     result.merge(acc)
 
     kwargs.setdefault("FCAL1Volumes",["LArMgr::LAr::FCAL::Module1::Gap"])
@@ -287,9 +296,12 @@ def LArHECSensitiveDetectorCfg(ConfigFlags, name="LArHECSensitiveDetector", **kw
     bare_collection_name = "LArHitHEC"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "LArHECHits"
-    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                                              mergeable_collection_suffix,
-                                                              merger_input_property)
+    region = "CALO"
+    acc, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                    bare_collection_name,
+                                                    mergeable_collection_suffix,
+                                                    merger_input_property,
+                                                    region)
     result.merge(acc)
 
     kwargs.setdefault("WheelVolumes",["LArMgr::LAr::HEC::Module::Depth::Slice"])
diff --git a/MuonSpectrometer/MuonG4/MuonG4SD/python/MuonG4SDConfig.py b/MuonSpectrometer/MuonG4/MuonG4SD/python/MuonG4SDConfig.py
index 8951047a9e4644f24c55ef8df7570c4f9b34183e..5bbb723dc026b7770be259892cf9f47c05add321 100644
--- a/MuonSpectrometer/MuonG4/MuonG4SD/python/MuonG4SDConfig.py
+++ b/MuonSpectrometer/MuonG4/MuonG4SD/python/MuonG4SDConfig.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 from AthenaCommon import CfgMgr
 
@@ -9,9 +9,11 @@ def getCSCSensitiveDetectorCosmics(name="CSCSensitiveDetectorCosmics", **kwargs)
     bare_collection_name = "CSC_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "CSCHits"
+    region = "MUON"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     kwargs.setdefault("LogicalVolumeNames", ["Muon::CscArCO2"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
     return CfgMgr.CSCSensitiveDetectorCosmicsTool(name, **kwargs)
@@ -21,9 +23,11 @@ def getCSCSensitiveDetector(name="CSCSensitiveDetector", **kwargs):
     bare_collection_name = "CSC_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "CSCHits"
+    region = "MUON"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     kwargs.setdefault("LogicalVolumeNames", ["Muon::CscArCO2"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
     return CfgMgr.CSCSensitiveDetectorTool(name, **kwargs)
@@ -39,9 +43,11 @@ def getMDTSensitiveDetectorCosmics(name="MDTSensitiveDetectorCosmics", **kwargs)
     bare_collection_name = "MDT_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "MDTHits"
+    region = "MUON"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     kwargs.setdefault("LogicalVolumeNames", ["Muon::SensitiveGas"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
     return CfgMgr.MDTSensitiveDetectorCosmicsTool(name, **kwargs)
@@ -51,9 +57,11 @@ def getMDTSensitiveDetector(name="MDTSensitiveDetector", **kwargs):
     bare_collection_name = "MDT_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "MDTHits"
+    region = "MUON"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     kwargs.setdefault("LogicalVolumeNames", ["Muon::SensitiveGas"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
     return CfgMgr.MDTSensitiveDetectorTool(name, **kwargs)
@@ -69,9 +77,11 @@ def getRPCSensitiveDetectorCosmics(name="RPCSensitiveDetectorCosmics", **kwargs)
     bare_collection_name = "RPC_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "RPCHits"
+    region = "MUON"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     kwargs.setdefault("LogicalVolumeNames", ["Muon::gazGap"])
     kwargs.setdefault("OutputCollectionNames", [bare_collection_name])
     return CfgMgr.RPCSensitiveDetectorCosmicsTool(name, **kwargs)
@@ -81,9 +91,11 @@ def getRPCSensitiveDetector(name="RPCSensitiveDetector", **kwargs):
     bare_collection_name = "RPC_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "RPCHits"
+    region = "MUON"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     kwargs.setdefault("LogicalVolumeNames", ["Muon::gazGap"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
     return CfgMgr.RPCSensitiveDetectorTool(name, **kwargs)
@@ -93,9 +105,11 @@ def getTGCSensitiveDetectorCosmics(name="TGCSensitiveDetectorCosmics", **kwargs)
     bare_collection_name = "TGC_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "TGCHits"
+    region = "MUON"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     kwargs.setdefault("LogicalVolumeNames", ["Muon::muo::TGCGas"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
     return CfgMgr.TGCSensitiveDetectorCosmicsTool(name, **kwargs)
@@ -105,9 +119,11 @@ def getTGCSensitiveDetector(name="TGCSensitiveDetector", **kwargs):
     bare_collection_name = "TGC_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "TGCHits"
+    region = "MUON"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     kwargs.setdefault("LogicalVolumeNames", ["Muon::muo::TGCGas"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
     return CfgMgr.TGCSensitiveDetectorTool(name, **kwargs)
diff --git a/MuonSpectrometer/MuonG4/MuonG4SD/python/MuonG4SDToolConfig.py b/MuonSpectrometer/MuonG4/MuonG4SD/python/MuonG4SDToolConfig.py
index 2141f9f5f5c2293ee242798d1c49384991a21911..e89eaea0c28c6266829398100f6db6619608e5db 100644
--- a/MuonSpectrometer/MuonG4/MuonG4SD/python/MuonG4SDToolConfig.py
+++ b/MuonSpectrometer/MuonG4/MuonG4SD/python/MuonG4SDToolConfig.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 from ISF_Algorithms.collection_merger_helpersNew import CollectionMergerCfg
 from AthenaConfiguration.ComponentFactory import CompFactory
 from AthenaConfiguration.ComponentAccumulator import ComponentAccumulator
@@ -9,9 +9,12 @@ def CSCSensitiveDetectorCosmicsCfg(ConfigFlags, name="CSCSensitiveDetectorCosmic
     bare_collection_name = "CSC_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "CSCHits"
-    result, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                                              mergeable_collection_suffix,
-                                                              merger_input_property)
+    region = "MUON"
+    result, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                       bare_collection_name,
+                                                       mergeable_collection_suffix,
+                                                       merger_input_property,
+                                                       region)
     kwargs.setdefault("LogicalVolumeNames", ["Muon::CscArCO2"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
 
@@ -21,9 +24,12 @@ def CSCSensitiveDetectorCfg(ConfigFlags, name="CSCSensitiveDetector", **kwargs):
     bare_collection_name = "CSC_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "CSCHits"
-    result, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                                              mergeable_collection_suffix,
-                                                              merger_input_property)
+    region = "MUON"
+    result, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                       bare_collection_name,
+                                                       mergeable_collection_suffix,
+                                                       merger_input_property,
+                                                       region)
     kwargs.setdefault("LogicalVolumeNames", ["Muon::CscArCO2"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
 
@@ -43,9 +49,12 @@ def MDTSensitiveDetectorCosmicsCfg(ConfigFlags, name="MDTSensitiveDetectorCosmic
     bare_collection_name = "MDT_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "MDTHits"
-    result, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                                              mergeable_collection_suffix,
-                                                              merger_input_property)
+    region = "MUON"
+    result, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                       bare_collection_name,
+                                                       mergeable_collection_suffix,
+                                                       merger_input_property,
+                                                       region)
     kwargs.setdefault("LogicalVolumeNames", ["Muon::SensitiveGas"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
 
@@ -57,9 +66,12 @@ def MDTSensitiveDetectorCfg(ConfigFlags, name="MDTSensitiveDetector", **kwargs):
     bare_collection_name = "MDT_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "MDTHits"
-    result, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                                              mergeable_collection_suffix,
-                                                              merger_input_property)
+    region = "MUON"
+    result, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                       bare_collection_name,
+                                                       mergeable_collection_suffix,
+                                                       merger_input_property,
+                                                       region)
     kwargs.setdefault("LogicalVolumeNames", ["Muon::SensitiveGas"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
 
@@ -69,7 +81,8 @@ def MDTSensitiveDetectorCfg(ConfigFlags, name="MDTSensitiveDetector", **kwargs):
 
 def MicromegasSensitiveDetectorCfg(ConfigFlags, name="MicromegasSensitiveDetector", **kwargs):
     kwargs.setdefault("LogicalVolumeNames", ["Muon::MM_Sensitive"])
-    kwargs.setdefault("OutputCollectionNames", ["MicromegasSensitiveDetector"]) # need ISF_Collection merger in acc?
+    kwargs.setdefault("OutputCollectionNames", ["MicromegasSensitiveDetector"])
+    # TODO add support for Micromegas to ISF_CollectionMerger
     result=ComponentAccumulator()
     result.setPrivateTools( MicromegasSensitiveDetectorTool(name, **kwargs) )
     return result
@@ -79,9 +92,12 @@ def RPCSensitiveDetectorCosmicsCfg(ConfigFlags, name="RPCSensitiveDetectorCosmic
     bare_collection_name = "RPC_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "RPCHits"
-    result, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                                              mergeable_collection_suffix,
-                                                              merger_input_property)
+    region = "MUON"
+    result, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                       bare_collection_name,
+                                                       mergeable_collection_suffix,
+                                                       merger_input_property,
+                                                       region)
     kwargs.setdefault("LogicalVolumeNames", ["Muon::gazGap"])
     kwargs.setdefault("OutputCollectionNames", [bare_collection_name]) #is this correct?
 
@@ -93,9 +109,12 @@ def RPCSensitiveDetectorCfg(ConfigFlags, name="RPCSensitiveDetector", **kwargs):
     bare_collection_name = "RPC_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "RPCHits"
-    result, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                                              mergeable_collection_suffix,
-                                                              merger_input_property)
+    region = "MUON"
+    result, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                       bare_collection_name,
+                                                       mergeable_collection_suffix,
+                                                       merger_input_property,
+                                                       region)
     kwargs.setdefault("LogicalVolumeNames", ["Muon::gazGap"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
 
@@ -107,9 +126,12 @@ def TGCSensitiveDetectorCosmicsCfg(ConfigFlags, name="TGCSensitiveDetectorCosmic
     bare_collection_name = "TGC_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "TGCHits"
-    result, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                                              mergeable_collection_suffix,
-                                                              merger_input_property)
+    region = "MUON"
+    result, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                       bare_collection_name,
+                                                       mergeable_collection_suffix,
+                                                       merger_input_property,
+                                                       region)
     kwargs.setdefault("LogicalVolumeNames", ["Muon::muo::TGCGas"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
 
@@ -121,9 +143,12 @@ def TGCSensitiveDetectorCfg(ConfigFlags, name="TGCSensitiveDetector", **kwargs):
     bare_collection_name = "TGC_Hits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "TGCHits"
-    result, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                                              mergeable_collection_suffix,
-                                                              merger_input_property)
+    region = "MUON"
+    result, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                       bare_collection_name,
+                                                       mergeable_collection_suffix,
+                                                       merger_input_property,
+                                                       region)
     kwargs.setdefault("LogicalVolumeNames", ["Muon::muo::TGCGas"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
 
@@ -134,7 +159,7 @@ def TGCSensitiveDetectorCfg(ConfigFlags, name="TGCSensitiveDetector", **kwargs):
 def sTGCSensitiveDetectorCfg(ConfigFlags, name="sTGCSensitiveDetector", **kwargs):
     kwargs.setdefault("LogicalVolumeNames", ["Muon::sTGC_Sensitive"])
     kwargs.setdefault("OutputCollectionNames", ["sTGCSensitiveDetector"])
-
+    # TODO add support for Micromegas to ISF_CollectionMerger
     result=ComponentAccumulator()
     result.setPrivateTools( sTGCSensitiveDetectorTool(name, **kwargs) )
     return result
diff --git a/Simulation/G4Atlas/G4AtlasApps/python/SimConfigFlags.py b/Simulation/G4Atlas/G4AtlasApps/python/SimConfigFlags.py
index 8155a366e6b12aa2c8031d04fca86d7787bf7ea4..2e6e1e4f2b3e1bd63aedb1fec557c813941b30da 100644
--- a/Simulation/G4Atlas/G4AtlasApps/python/SimConfigFlags.py
+++ b/Simulation/G4Atlas/G4AtlasApps/python/SimConfigFlags.py
@@ -77,7 +77,7 @@ def createSimConfigFlags():
 
     # For ISF
     scf.addFlag("Sim.ISFRun",False)
-    scf.addFlag("Sim.ISF.HITSMergingRequired", True)
+    scf.addFlag("Sim.ISF.HITSMergingRequired", {'ID':True, 'CALO':True, 'MUON':True})
     scf.addFlag("Sim.ISF.Simulator", "ATLFASTII")
     scf.addFlag("Sim.ISF.DoTimeMonitoring", True) # bool: run time monitoring
     scf.addFlag("Sim.ISF.DoMemoryMonitoring", True) # bool: run time monitoring
diff --git a/Simulation/ISF/ISF_Config/python/FlagSetters.py b/Simulation/ISF/ISF_Config/python/FlagSetters.py
index b3922c80ef86d013f4fd46961b7d91b99f669650..348a9d8109c3cc6e9466b490c236e99f8e5cc0f0 100644
--- a/Simulation/ISF/ISF_Config/python/FlagSetters.py
+++ b/Simulation/ISF/ISF_Config/python/FlagSetters.py
@@ -46,7 +46,8 @@ def configureFlagsBase():
 def configureFlagsFullG4():
     from G4AtlasApps.SimFlags import simFlags
     simFlags.SimulationFlavour = "FullG4"
-    ISF_Flags.HITSMergingRequired = False
+    mergeDict = {'ID':False, 'CALO':False, 'MUON':False}
+    ISF_Flags.HITSMergingRequired.get_Value().update(mergeDict)
     ISF_Flags.ParticleBroker = "ISF_ParticleBrokerSvcNoOrdering"
     return
 
@@ -126,6 +127,8 @@ def configureFlagsATLFASTII():
     simFlags.SimulationFlavour = "AtlfastII" # TODO: can we rename this to "ATLFASTII" ?
     from ISF_Config.ISF_jobProperties import ISF_Flags
     ISF_Flags.UsingGeant4 = True
+    mergeDict = {'ID':False, 'CALO':True, 'MUON':False}
+    ISF_Flags.HITSMergingRequired.get_Value().update(mergeDict)
     ISF_Flags.ParticleBroker = "ISF_AFIIParticleBrokerSvc"
     return
 
@@ -179,6 +182,9 @@ def configureFlagsATLFASTIIF():
     from TrkDetDescrSvc.TrkDetDescrJobProperties import TrkDetFlags
     TrkDetFlags.MaterialVersion=21
     TrkDetFlags.TRT_BuildStrawLayers=True
+    from ISF_Config.ISF_jobProperties import ISF_Flags
+    mergeDict = {'ID':True, 'CALO':True, 'MUON':True}
+    ISF_Flags.HITSMergingRequired.get_Value().update(mergeDict)
     return
 
 def configureFlagsATLFASTIIFMT():
@@ -212,6 +218,9 @@ def configureFlagsG4HS_FastPileup():
     from TrkDetDescrSvc.TrkDetDescrJobProperties import TrkDetFlags
     TrkDetFlags.MaterialVersion=21
     TrkDetFlags.TRT_BuildStrawLayers=True
+    from ISF_Config.ISF_jobProperties import ISF_Flags
+    mergeDict = {'ID':True, 'CALO':True, 'MUON':True}
+    ISF_Flags.HITSMergingRequired.get_Value().update(mergeDict)
     return
 
 def configureFlagsATLFASTIIF_IDOnly():
@@ -244,6 +253,8 @@ def configureFlagsATLFASTIIF_G4MS():
 def configureFlagsMultiSimTest():
     from ISF_Config.ISF_jobProperties import ISF_Flags
     ISF_Flags.UsingGeant4 = True
+    mergeDict = {'ID':True, 'CALO':True, 'MUON':True}
+    ISF_Flags.HITSMergingRequired.get_Value().update(mergeDict)
     return
 
 def configureFlagsG4GammaCones():
diff --git a/Simulation/ISF/ISF_Config/python/ISF_jobProperties.py b/Simulation/ISF/ISF_Config/python/ISF_jobProperties.py
index 1dd7c0fb9c9481c45fd0f67e73139d26bae26ac2..5878594eb542d7ea8febca1018377b2541e7fdef 100644
--- a/Simulation/ISF/ISF_Config/python/ISF_jobProperties.py
+++ b/Simulation/ISF/ISF_Config/python/ISF_jobProperties.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 ## @file ISF_Config/python/ISF_jobProperties.py
 ## @brief Python module to hold common flags to configure JobOptions
@@ -109,8 +109,13 @@ class Simulator(JobProperty):
 class HITSMergingRequired(JobProperty):
     """The configured set of simulators requires merging of HITS collections"""
     statusOn     = True
-    allowedTypes = ['bool']
-    StoredValue  = True
+    allowedTypes = ['dict']
+    StoredValue = {'ID':True, 'CALO':True, 'MUON':True}
+    def anyOn(self):
+        if self.statusOn:
+            return (True in self.StoredValue.values())
+        else:
+            return False
 
 class UsingGeant4(JobProperty):
     """Will this job be using Geant4?"""
diff --git a/Simulation/ISF/ISF_Config/share/ISF_ConfigJobInclude.py b/Simulation/ISF/ISF_Config/share/ISF_ConfigJobInclude.py
index 6ad25b64c2cea50038562810c651915b1b0f77bc..053b60a529b3974e9f9ad4804058e9cb6445497f 100644
--- a/Simulation/ISF/ISF_Config/share/ISF_ConfigJobInclude.py
+++ b/Simulation/ISF/ISF_Config/share/ISF_ConfigJobInclude.py
@@ -168,7 +168,7 @@ from ISF_Example.ISF_Metadata import createSimulationParametersMetadata, configu
 createSimulationParametersMetadata()
 configureRunNumberOverrides()
 
-if ISF_Flags.HITSMergingRequired():
+if ISF_Flags.HITSMergingRequired.anyOn():
     topSequence += collection_merger_alg
 
 #--------------------------------------------------------------
diff --git a/Simulation/ISF/ISF_Config/test/test_Sim_tf_configuration.py b/Simulation/ISF/ISF_Config/test/test_Sim_tf_configuration.py
index 71b59344e23ac403d75e670d0a7314323a37a17e..c2f2f9c6cc71411071939061b268533c0a321a60 100755
--- a/Simulation/ISF/ISF_Config/test/test_Sim_tf_configuration.py
+++ b/Simulation/ISF/ISF_Config/test/test_Sim_tf_configuration.py
@@ -65,19 +65,19 @@ class TestATLFASTII(unittest.TestCase):
                          actual_last_ath_alg_sequence_entry)
 
     def test___ISF_Collection_merger_InputBCMHits_contains_only_G4_collection(self):
-        expected_input_hits = ['BCMHits_G4']
+        expected_input_hits = []
         self._assert_ISF_CollectionMerger_property_unordered_equal(
             'InputBCMHits',
             expected_input_hits)
 
     def test___ISF_Collection_merger_InputBLMHits_contains_only_G4_collection(self):
-        expected_input_hits = ['BLMHits_G4']
+        expected_input_hits = []
         self._assert_ISF_CollectionMerger_property_unordered_equal(
             'InputBLMHits',
             expected_input_hits)
 
     def test___ISF_Collection_merger_InputCSCHits_contains_only_G4_collection(self):
-        expected_input_hits = ['CSC_Hits_G4']
+        expected_input_hits = []
         self._assert_ISF_CollectionMerger_property_unordered_equal(
             'InputCSCHits',
             expected_input_hits)
@@ -113,37 +113,37 @@ class TestATLFASTII(unittest.TestCase):
             expected_input_hits)
 
     def test___ISF_Collection_merger_InputMDTHits_contains_only_G4_collection(self):
-        expected_input_hits = ['MDT_Hits_G4']
+        expected_input_hits = []
         self._assert_ISF_CollectionMerger_property_unordered_equal(
             'InputMDTHits',
             expected_input_hits)
 
     def test___ISF_Collection_merger_InputPixelHits_contains_only_G4_collection(self):
-        expected_input_hits = ['PixelHits_G4']
+        expected_input_hits = []
         self._assert_ISF_CollectionMerger_property_unordered_equal(
             'InputPixelHits',
             expected_input_hits)
 
     def test___ISF_Collection_merger_InputRPCHits_contains_only_G4_collection(self):
-        expected_input_hits = ['RPC_Hits_G4']
+        expected_input_hits = []
         self._assert_ISF_CollectionMerger_property_unordered_equal(
             'InputRPCHits',
             expected_input_hits)
 
     def test___ISF_Collection_merger_InputSCTHits_contains_only_G4_collection(self):
-        expected_input_hits = ['SCT_Hits_G4']
+        expected_input_hits = []
         self._assert_ISF_CollectionMerger_property_unordered_equal(
             'InputSCTHits',
             expected_input_hits)
 
     def test___ISF_Collection_merger_InputTGCHits_contains_only_G4_collection(self):
-        expected_input_hits = ['TGC_Hits_G4']
+        expected_input_hits = []
         self._assert_ISF_CollectionMerger_property_unordered_equal(
             'InputTGCHits',
             expected_input_hits)
 
     def test___ISF_Collection_merger_InputTRTUncompressedHits_contains_only_G4_collection(self):
-        expected_input_hits = ['TRTUncompressedHits_G4']
+        expected_input_hits = []
         self._assert_ISF_CollectionMerger_property_unordered_equal(
             'InputTRTUncompressedHits',
             expected_input_hits)
diff --git a/Simulation/ISF/ISF_Core/ISF_Algorithms/python/collection_merger_helpers.py b/Simulation/ISF/ISF_Core/ISF_Algorithms/python/collection_merger_helpers.py
index 7335385ccf145dc2a9579644c607a35cc0e2a929..7f558ad10f2bb69c09b9eae8f7b7263e7feb2dd9 100644
--- a/Simulation/ISF/ISF_Core/ISF_Algorithms/python/collection_merger_helpers.py
+++ b/Simulation/ISF/ISF_Core/ISF_Algorithms/python/collection_merger_helpers.py
@@ -6,7 +6,8 @@ from AthenaCommon.AthenaCommonFlags import athenaCommonFlags
 
 def generate_mergeable_collection_name(bare_collection_name,
                                        mergeable_collection_suffix,
-                                       merger_input_property):
+                                       merger_input_property,
+                                       region):
     """
     Generates and returns a collection name that is also registered to
     the ISF CollectionMerger algorithm.
@@ -19,7 +20,7 @@ def generate_mergeable_collection_name(bare_collection_name,
         CollectionMerger algorithm to add the mergeable collection to.
     """
     hardscatterSG = "OriginalEvent_SG+"
-    if simFlags.ISFRun() and ISF_Flags.HITSMergingRequired():
+    if simFlags.ISFRun() and ISF_Flags.HITSMergingRequired.get_Value().get(region,True):
         mergeable_collection = '{bare}{suffix}'.format(
             bare=bare_collection_name,
             suffix=mergeable_collection_suffix
diff --git a/Simulation/ISF/ISF_Core/ISF_Algorithms/python/collection_merger_helpersNew.py b/Simulation/ISF/ISF_Core/ISF_Algorithms/python/collection_merger_helpersNew.py
index 3756a6a0de370a7592b09fabeeea74a3eed66b57..c9934f5f5621b168a6230130e6a2181de908bf80 100644
--- a/Simulation/ISF/ISF_Core/ISF_Algorithms/python/collection_merger_helpersNew.py
+++ b/Simulation/ISF/ISF_Core/ISF_Algorithms/python/collection_merger_helpersNew.py
@@ -1,15 +1,17 @@
-# Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 from __future__ import print_function
 
 from AthenaConfiguration.ComponentAccumulator import ComponentAccumulator
 
-def CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                        mergeable_collection_suffix,
-                                        merger_input_property):
+def CollectionMergerCfg(ConfigFlags,
+                        bare_collection_name,
+                        mergeable_collection_suffix,
+                        merger_input_property,
+                        region):
   """Generates and returns a collection name that is also registered to
      the ISF CollectionMerger algorithm.
- 
+
      :param bare_collection_name: name of the collection if no merging
          is taking place.
      :param mergeable_collection_suffix: suffix to the collection in
@@ -18,18 +20,18 @@ def CollectionMergerCfg(ConfigFlags, bare_collection_name,
          CollectionMerger algorithm to add the mergeable collection to."""
 
   result = ComponentAccumulator()
-  if ConfigFlags.Sim.ISFRun and ConfigFlags.Sim.ISF.HITSMergingRequired: 
+  if ConfigFlags.Sim.ISFRun and ConfigFlags.Sim.ISF.HITSMergingRequired.get(region,True):
       mergeable_collection = '{bare}{suffix}'.format(
              bare=bare_collection_name,
              suffix=mergeable_collection_suffix)
-         
+
       from ISF_Algorithms.CollectionMergerConfig import ISFCollectionMergerCfg
       algo=ISFCollectionMergerCfg(ConfigFlags)
       result.addEventAlgo(algo)
 
       input_attribute_name = 'Input{merger_input_property}'.format(
       merger_input_property=merger_input_property)
-    
+
       merger_input_collections = getattr(algo,input_attribute_name) #empty list always?
       merger_input_collections.append(mergeable_collection)
 
diff --git a/Simulation/ISF/ISF_Core/ISF_Algorithms/python/test/test_collection_merger_helpers.py b/Simulation/ISF/ISF_Core/ISF_Algorithms/python/test/test_collection_merger_helpers.py
index c7c2a069759840ad5f36892d205e940594b087d2..41854bf88efab457a1b28fb5aa08f3398abe3f9e 100755
--- a/Simulation/ISF/ISF_Core/ISF_Algorithms/python/test/test_collection_merger_helpers.py
+++ b/Simulation/ISF/ISF_Core/ISF_Algorithms/python/test/test_collection_merger_helpers.py
@@ -22,28 +22,34 @@ class Test_generate_mergeable_collection_name(unittest.TestCase):
 
     def test_isISFRunAndHITSMergingRequired_expectBareNameWithSuffixReturned(self):
         simFlags.ISFRun.set_Value(True)
-        ISF_Flags.HITSMergingRequired.set_Value(True)
+        mergeDict = {'ID':True, 'CALO':True, 'MUON':True}
+        ISF_Flags.HITSMergingRequired.get_Value().update(mergeDict)
 
         bare_collection_name = 'aTestCollection'
         collection_suffix = '_TESTSUFFIX'
         merger_input_property = 'PixelHits'
+        region = 'ID'
         actual_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                                     collection_suffix,
-                                                                    merger_input_property)
+                                                                    merger_input_property,
+                                                                    region)
 
         expected_collection_name = 'aTestCollection_TESTSUFFIX'
         self.assertEqual(expected_collection_name, actual_collection_name)
 
     def test_isISFRunAndHITSMergingRequiredWithEmptyCollectionMergerAlgorithm_expectCollectionAddedToCollectionMergerAlgorithm(self):
         simFlags.ISFRun.set_Value(True)
-        ISF_Flags.HITSMergingRequired.set_Value(True)
+        mergeDict = {'ID':True, 'CALO':True, 'MUON':True}
+        ISF_Flags.HITSMergingRequired.get_Value().update(mergeDict)
 
         bare_collection_name = 'aTestCollection'
         collection_suffix = '_TESTSUFFIX'
         merger_input_property = 'PixelHits'
+        region = 'ID'
         actual_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                                     collection_suffix,
-                                                                    merger_input_property)
+                                                                    merger_input_property,
+                                                                    region)
 
         collection_merger = getAlgorithm('ISF_CollectionMerger')
         actual_collection_merger_input = collection_merger.InputPixelHits
@@ -54,28 +60,34 @@ class Test_generate_mergeable_collection_name(unittest.TestCase):
 
     def test_isISFRunAndNoHITSMergingRequired_expectBareCollectionNameReturned(self):
         simFlags.ISFRun.set_Value(True)
-        ISF_Flags.HITSMergingRequired.set_Value(False)
+        mergeDict = {'ID':False, 'CALO':True, 'MUON':False}
+        ISF_Flags.HITSMergingRequired.get_Value().update(mergeDict)
 
         bare_collection_name = 'aTestCollection'
         collection_suffix = '_TESTSUFFIX'
         merger_input_property = 'PixelHits'
+        region = 'ID'
         actual_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                                     collection_suffix,
-                                                                    merger_input_property)
+                                                                    merger_input_property,
+                                                                    region)
 
         expected_collection_name = 'aTestCollection'
         self.assertEqual(expected_collection_name, actual_collection_name)
 
     def test_isISFRunAndNoHITSMergingRequiredWithEmptyCollectionMergerAlgorithm_expectCollectionMergerAlgorithmUntouched(self):
         simFlags.ISFRun.set_Value(True)
-        ISF_Flags.HITSMergingRequired.set_Value(False)
+        mergeDict = {'ID':False, 'CALO':True, 'MUON':False}
+        ISF_Flags.HITSMergingRequired.get_Value().update(mergeDict)
 
         bare_collection_name = 'aTestCollection'
         collection_suffix = '_TESTSUFFIX'
         merger_input_property = 'PixelHits'
+        region = 'ID'
         actual_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                                     collection_suffix,
-                                                                    merger_input_property)
+                                                                    merger_input_property,
+                                                                    region)
 
         collection_merger = getAlgorithm('ISF_CollectionMerger')
         actual_collection_merger_input = collection_merger.InputPixelHits
@@ -86,42 +98,51 @@ class Test_generate_mergeable_collection_name(unittest.TestCase):
 
     def test_isNotISFRunAndNoHITSMergingRequired_expectBareCollectioNameReturned(self):
         simFlags.ISFRun.set_Value(False)
-        ISF_Flags.HITSMergingRequired.set_Value(False)
+        mergeDict = {'ID':False, 'CALO':True, 'MUON':False}
+        ISF_Flags.HITSMergingRequired.get_Value().update(mergeDict)
 
         bare_collection_name = 'aTestCollection'
         collection_suffix = '_TESTSUFFIX'
         merger_input_property = 'PixelHits'
+        region = 'ID'
         actual_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                                     collection_suffix,
-                                                                    merger_input_property)
+                                                                    merger_input_property,
+                                                                    region)
 
         expected_collection_name = 'aTestCollection'
         self.assertEqual(expected_collection_name, actual_collection_name)
 
     def test_isNotISFRunAndHITSMergingRequired_expectBareCollectioNameReturned(self):
         simFlags.ISFRun.set_Value(False)
-        ISF_Flags.HITSMergingRequired.set_Value(True)
+        mergeDict = {'ID':True, 'CALO':True, 'MUON':True}
+        ISF_Flags.HITSMergingRequired.get_Value().update(mergeDict)
 
         bare_collection_name = 'aTestCollection'
         collection_suffix = '_TESTSUFFIX'
         merger_input_property = 'PixelHits'
+        region = 'ID'
         actual_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                                     collection_suffix,
-                                                                    merger_input_property)
+                                                                    merger_input_property,
+                                                                    region)
 
         expected_collection_name = 'aTestCollection'
         self.assertEqual(expected_collection_name, actual_collection_name)
 
     def test_isNotISFRunAndNoHITSMergingRequired_expectCollectionMergerAlgorithmUntouched(self):
         simFlags.ISFRun.set_Value(False)
-        ISF_Flags.HITSMergingRequired.set_Value(False)
+        mergeDict = {'ID':True, 'CALO':True, 'MUON':True}
+        ISF_Flags.HITSMergingRequired.get_Value().update(mergeDict)
 
         bare_collection_name = 'aTestCollection'
         collection_suffix = '_TESTSUFFIX'
         merger_input_property = 'PixelHits'
+        region = 'ID'
         actual_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                                     collection_suffix,
-                                                                    merger_input_property)
+                                                                    merger_input_property,
+                                                                    region)
 
         collection_merger = getAlgorithm('ISF_CollectionMerger')
         actual_collection_merger_input = collection_merger.InputPixelHits
@@ -132,14 +153,17 @@ class Test_generate_mergeable_collection_name(unittest.TestCase):
 
     def test_isNotISFRunAndHITSMergingRequired_expectCollectionMergerAlgorithmUntouched(self):
         simFlags.ISFRun.set_Value(False)
-        ISF_Flags.HITSMergingRequired.set_Value(True)
+        mergeDict = {'ID':True, 'CALO':True, 'MUON':True}
+        ISF_Flags.HITSMergingRequired.get_Value().update(mergeDict)
 
         bare_collection_name = 'aTestCollection'
         collection_suffix = '_TESTSUFFIX'
         merger_input_property = 'PixelHits'
+        region = 'ID'
         actual_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                                     collection_suffix,
-                                                                    merger_input_property)
+                                                                    merger_input_property,
+                                                                    region)
 
         collection_merger = getAlgorithm('ISF_CollectionMerger')
         actual_collection_merger_input = collection_merger.InputPixelHits
diff --git a/Simulation/ISF/ISF_FastCaloSim/ISF_FastCaloSimServices/python/AdditionalConfig.py b/Simulation/ISF/ISF_FastCaloSim/ISF_FastCaloSimServices/python/AdditionalConfig.py
index 965d5cf9833a3259fa3bb23b2fa4e25524ae468f..b3377782370c9d963c60001b53ebbdf96b8dc58b 100644
--- a/Simulation/ISF/ISF_FastCaloSim/ISF_FastCaloSimServices/python/AdditionalConfig.py
+++ b/Simulation/ISF/ISF_FastCaloSim/ISF_FastCaloSimServices/python/AdditionalConfig.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 """
 Tools configurations for ISF_FastCaloSimServices
@@ -801,41 +801,47 @@ def getPileupFastShowerCellBuilderTool(name="ISF_PileupFastShowerCellBuilderTool
 
 def getFastHitConvertTool(name="ISF_FastHitConvertTool", **kwargs):
     mergeable_collection_suffix = "_FastCaloSim"
+    region = "CALO"
 
     EMB_hits_bare_collection_name = "LArHitEMB"
     EMB_hits_merger_input_property = "LArEMBHits"
     EMB_hits_collection_name = generate_mergeable_collection_name(
         EMB_hits_bare_collection_name,
         mergeable_collection_suffix,
-        EMB_hits_merger_input_property)
+        EMB_hits_merger_input_property,
+        region)
 
     EMEC_hits_bare_collection_name = "LArHitEMEC"
     EMEC_hits_merger_input_property = "LArEMECHits"
     EMEC_hits_collection_name = generate_mergeable_collection_name(
         EMEC_hits_bare_collection_name,
         mergeable_collection_suffix,
-        EMEC_hits_merger_input_property)
+        EMEC_hits_merger_input_property,
+        region)
 
     FCAL_hits_bare_collection_name = "LArHitFCAL"
     FCAL_hits_merger_input_property = "LArFCALHits"
     FCAL_hits_collection_name = generate_mergeable_collection_name(
         FCAL_hits_bare_collection_name,
         mergeable_collection_suffix,
-        FCAL_hits_merger_input_property)
+        FCAL_hits_merger_input_property,
+        region)
 
     HEC_hits_bare_collection_name = "LArHitHEC"
     HEC_hits_merger_input_property = "LArHECHits"
     HEC_hits_collection_name = generate_mergeable_collection_name(
         HEC_hits_bare_collection_name,
         mergeable_collection_suffix,
-        HEC_hits_merger_input_property)
+        HEC_hits_merger_input_property,
+        region)
 
     tile_hits_bare_collection_name = "TileHitVec"
     tile_hits_merger_input_property = "TileHits"
     tile_hits_collection_name = generate_mergeable_collection_name(
         tile_hits_bare_collection_name,
         mergeable_collection_suffix,
-        tile_hits_merger_input_property)
+        tile_hits_merger_input_property,
+        region)
 
     kwargs.setdefault('embHitContainername', EMB_hits_collection_name)
     kwargs.setdefault('emecHitContainername', EMEC_hits_collection_name)
diff --git a/Simulation/ISF/ISF_FastCaloSim/ISF_FastCaloSimServices/python/ISF_FastCaloSimServicesConfigNew.py b/Simulation/ISF/ISF_FastCaloSim/ISF_FastCaloSimServices/python/ISF_FastCaloSimServicesConfigNew.py
index a7b7b92c50daa7b38c6713c3e83536925d575f4d..f4ae1166ab9bc980e076dddd7ca66daa5875874c 100644
--- a/Simulation/ISF/ISF_FastCaloSim/ISF_FastCaloSimServices/python/ISF_FastCaloSimServicesConfigNew.py
+++ b/Simulation/ISF/ISF_FastCaloSim/ISF_FastCaloSimServices/python/ISF_FastCaloSimServicesConfigNew.py
@@ -111,6 +111,7 @@ def FastHitConvertToolCfg(flags, name="ISF_FastHitConvertTool", **kwargs):
 
     acc = ComponentAccumulator()
     mergeable_collection_suffix = "_FastCaloSim"
+    region = "CALO"
 
     EMB_hits_bare_collection_name = "LArHitEMB"
     EMB_hits_merger_input_property = "LArEMBHits"
@@ -118,7 +119,8 @@ def FastHitConvertToolCfg(flags, name="ISF_FastHitConvertTool", **kwargs):
         flags,
         EMB_hits_bare_collection_name,
         mergeable_collection_suffix,
-        EMB_hits_merger_input_property)
+        EMB_hits_merger_input_property,
+        region)
     acc.merge(acc1)
 
     EMEC_hits_bare_collection_name = "LArHitEMEC"
@@ -127,7 +129,8 @@ def FastHitConvertToolCfg(flags, name="ISF_FastHitConvertTool", **kwargs):
         flags,
         EMEC_hits_bare_collection_name,
         mergeable_collection_suffix,
-        EMEC_hits_merger_input_property)
+        EMEC_hits_merger_input_property,
+        region)
     acc.merge(acc2)
 
     FCAL_hits_bare_collection_name = "LArHitFCAL"
@@ -136,7 +139,8 @@ def FastHitConvertToolCfg(flags, name="ISF_FastHitConvertTool", **kwargs):
         flags,
         FCAL_hits_bare_collection_name,
         mergeable_collection_suffix,
-        FCAL_hits_merger_input_property)
+        FCAL_hits_merger_input_property,
+        region)
     acc.merge(acc3)
 
     HEC_hits_bare_collection_name = "LArHitHEC"
@@ -145,7 +149,8 @@ def FastHitConvertToolCfg(flags, name="ISF_FastHitConvertTool", **kwargs):
         flags,
         HEC_hits_bare_collection_name,
         mergeable_collection_suffix,
-        HEC_hits_merger_input_property)
+        HEC_hits_merger_input_property,
+        region)
     acc.merge(acc4)
 
     tile_hits_bare_collection_name = "TileHitVec"
@@ -154,7 +159,8 @@ def FastHitConvertToolCfg(flags, name="ISF_FastHitConvertTool", **kwargs):
         flags,
         tile_hits_bare_collection_name,
         mergeable_collection_suffix,
-        tile_hits_merger_input_property)
+        tile_hits_merger_input_property,
+        region)
     acc.merge(acc5)
 
     kwargs.setdefault("embHitContainername", EMB_hits_collection_name)
diff --git a/Simulation/ISF/ISF_Fatras/ISF_FatrasServices/python/ISF_FatrasServicesConfig.py b/Simulation/ISF/ISF_Fatras/ISF_FatrasServices/python/ISF_FatrasServicesConfig.py
index 88d3c195bc7c78979b699a1ec3cfadd93947bc40..e705869167ef6917e505012318933df652a12edb 100644
--- a/Simulation/ISF/ISF_Fatras/ISF_FatrasServices/python/ISF_FatrasServicesConfig.py
+++ b/Simulation/ISF/ISF_Fatras/ISF_FatrasServices/python/ISF_FatrasServicesConfig.py
@@ -530,9 +530,11 @@ def getFatrasHitCreatorPixel(name="ISF_FatrasHitCreatorPixel", **kwargs):
     bare_collection_name = "PixelHits"
     mergeable_collection_suffix = "_Fatras"
     merger_input_property = "PixelHits"
+    region = 'ID'
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
 
     from G4AtlasApps.SimFlags import simFlags
     kwargs.setdefault("RandomNumberService" , simFlags.RandomSvc() )
@@ -549,9 +551,11 @@ def getFatrasHitCreatorSCT(name="ISF_FatrasHitCreatorSCT", **kwargs):
     bare_collection_name = "SCT_Hits"
     mergeable_collection_suffix = "_Fatras"
     merger_input_property = "SCTHits"
+    region = 'ID'
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     from G4AtlasApps.SimFlags import simFlags
     kwargs.setdefault("RandomNumberService" , simFlags.RandomSvc() )
     kwargs.setdefault("RandomStreamName"    , ISF_FatrasFlags.RandomStreamName())
@@ -566,9 +570,11 @@ def getFatrasHitCreatorTRT(name="ISF_FatrasHitCreatorTRT", **kwargs):
     bare_collection_name = "TRTUncompressedHits"
     mergeable_collection_suffix = "_Fatras"
     merger_input_property = "TRTUncompressedHits"
+    region = 'ID'
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     from G4AtlasApps.SimFlags import simFlags
     kwargs.setdefault("RandomNumberService" , simFlags.RandomSvc() )
     kwargs.setdefault("RandomStreamName"    , ISF_FatrasFlags.RandomStreamName())
@@ -609,27 +615,32 @@ def getFatrasPileupSimHitCreatorID(name="ISF_FatrasPileupSimHitCreatorID", **kwa
 
 def getFatrasSimHitCreatorMS(name="ISF_FatrasSimHitCreatorMS", **kwargs):
     mergeable_collection_suffix = "_Fatras"
+    region = 'MUON'
 
     mdt_bare_collection_name = "MDT_Hits"
     mdt_merger_input_property = "MDTHits"
     mdt_hits_collection_name = generate_mergeable_collection_name(mdt_bare_collection_name,
                                                                   mergeable_collection_suffix,
-                                                                  mdt_merger_input_property)
+                                                                  mdt_merger_input_property,
+                                                                  region)
     rpc_bare_collection_name = "RPC_Hits"
     rpc_merger_input_property = "RPCHits"
     rpc_hits_collection_name = generate_mergeable_collection_name(rpc_bare_collection_name,
                                                                   mergeable_collection_suffix,
-                                                                  rpc_merger_input_property)
+                                                                  rpc_merger_input_property,
+                                                                  region)
     tgc_bare_collection_name = "TGC_Hits"
     tgc_merger_input_property = "TGCHits"
     tgc_hits_collection_name = generate_mergeable_collection_name(tgc_bare_collection_name,
                                                                   mergeable_collection_suffix,
-                                                                  tgc_merger_input_property)
+                                                                  tgc_merger_input_property,
+                                                                  region)
     csc_bare_collection_name = "CSC_Hits"
     csc_merger_input_property = "CSCHits"
     csc_hits_collection_name = generate_mergeable_collection_name(csc_bare_collection_name,
                                                                   mergeable_collection_suffix,
-                                                                  csc_merger_input_property)
+                                                                  csc_merger_input_property,
+                                                                  region)
 
     from G4AtlasApps.SimFlags import simFlags
     kwargs.setdefault("RandomNumberService" , simFlags.RandomSvc() )
diff --git a/TileCalorimeter/TileG4/TileAncillary/MinBiasScintillator/python/MinBiasScintillatorConfig.py b/TileCalorimeter/TileG4/TileAncillary/MinBiasScintillator/python/MinBiasScintillatorConfig.py
index ad1193366c7515a9eccc907a2ceb3f79d01a4d7f..5701f69bd18fdd2e6fdbec1a711ff55a9b1e560c 100644
--- a/TileCalorimeter/TileG4/TileAncillary/MinBiasScintillator/python/MinBiasScintillatorConfig.py
+++ b/TileCalorimeter/TileG4/TileAncillary/MinBiasScintillator/python/MinBiasScintillatorConfig.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 from AthenaCommon import CfgMgr
 
@@ -9,9 +9,11 @@ def getMinBiasScintillatorSD(name="MinBiasScintillatorSD", **kwargs):
     bare_collection_name = "MBTSHits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "MBTSHits"
+    region = "CALO"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     kwargs.setdefault("LogicalVolumeNames", ["LArMgr::MBTS1", "LArMgr::MBTS2"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
     from G4AtlasApps.SimFlags import simFlags
diff --git a/TileCalorimeter/TileG4/TileAncillary/MinBiasScintillator/python/MinBiasScintillatorToolConfig.py b/TileCalorimeter/TileG4/TileAncillary/MinBiasScintillator/python/MinBiasScintillatorToolConfig.py
index eff199174cf5f14e6795d01c110d7538fd0e3a21..def341b6f0a31aa02be9a41b9b72ead2b9d30505 100644
--- a/TileCalorimeter/TileG4/TileAncillary/MinBiasScintillator/python/MinBiasScintillatorToolConfig.py
+++ b/TileCalorimeter/TileG4/TileAncillary/MinBiasScintillator/python/MinBiasScintillatorToolConfig.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 from ISF_Algorithms.collection_merger_helpersNew import CollectionMergerCfg
 from AthenaConfiguration.ComponentFactory import CompFactory
@@ -9,10 +9,13 @@ def MinBiasScintillatorSDCfg(ConfigFlags, name="MinBiasScintillatorSD", **kwargs
     bare_collection_name = "MBTSHits"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "MBTSHits"
+    region = "CALO"
 
-    result, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name,
-                                                              mergeable_collection_suffix,
-                                                              merger_input_property)
+    result, hits_collection_name = CollectionMergerCfg(ConfigFlags,
+                                                       bare_collection_name,
+                                                       mergeable_collection_suffix,
+                                                       merger_input_property,
+                                                       region)
     kwargs.setdefault("LogicalVolumeNames", ["LArMgr::MBTS1", "LArMgr::MBTS2"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
 
@@ -20,6 +23,6 @@ def MinBiasScintillatorSDCfg(ConfigFlags, name="MinBiasScintillatorSD", **kwargs
         kwargs.setdefault("DeltaTHit", [1])
         kwargs.setdefault("DoTOFCorrection", False)
 
-    result.setPrivateTools( MinBiasScintillatorSDTool(name, **kwargs) ) 
+    result.setPrivateTools( MinBiasScintillatorSDTool(name, **kwargs) )
 
     return result
diff --git a/TileCalorimeter/TileG4/TileGeoG4SD/python/TileGeoG4SDConfig.py b/TileCalorimeter/TileG4/TileGeoG4SD/python/TileGeoG4SDConfig.py
index 9f53ee840cdeee5d3fd02d8ac8543b2777f4d2a8..6fcc691780e44629fb9180f162efba3133e60721 100644
--- a/TileCalorimeter/TileG4/TileGeoG4SD/python/TileGeoG4SDConfig.py
+++ b/TileCalorimeter/TileG4/TileGeoG4SD/python/TileGeoG4SDConfig.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2002-2018 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 from AthenaCommon import CfgMgr
 
@@ -9,9 +9,11 @@ def getTileGeoG4SD(name="TileGeoG4SD", **kwargs):
     bare_collection_name = "TileHitVec"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "TileHits"
+    region = "CALO"
     hits_collection_name = generate_mergeable_collection_name(bare_collection_name,
                                                               mergeable_collection_suffix,
-                                                              merger_input_property)
+                                                              merger_input_property,
+                                                              region)
     kwargs.setdefault("LogicalVolumeNames", ["Tile::Scintillator"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
     return CfgMgr.TileGeoG4SDTool(name, **kwargs)
diff --git a/TileCalorimeter/TileG4/TileGeoG4SD/python/TileGeoG4SDToolConfig.py b/TileCalorimeter/TileG4/TileGeoG4SD/python/TileGeoG4SDToolConfig.py
index 95a634d93bfadc6bcf092d1f5385b8579db07a38..44a5949671bd7a0a2914de93053baaf2e15d515d 100644
--- a/TileCalorimeter/TileG4/TileGeoG4SD/python/TileGeoG4SDToolConfig.py
+++ b/TileCalorimeter/TileG4/TileGeoG4SD/python/TileGeoG4SDToolConfig.py
@@ -10,11 +10,15 @@ def TileGeoG4SDCfg(ConfigFlags, name="TileGeoG4SD", **kwargs):
     bare_collection_name = "TileHitVec"
     mergeable_collection_suffix = "_G4"
     merger_input_property = "TileHits"
+    region = "CALO"
 
-    result, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name, mergeable_collection_suffix, merger_input_property)
+    result, hits_collection_name = CollectionMergerCfg(ConfigFlags, bare_collection_name, mergeable_collection_suffix, merger_input_property, region)
     kwargs.setdefault("LogicalVolumeNames", ["Tile::Scintillator"])
     kwargs.setdefault("OutputCollectionNames", [hits_collection_name])
 
+    result.merge(TileGeoG4SDCalcCfg(ConfigFlags))
+    kwargs.setdefault("TileCalculator", result.getService("TileGeoG4SDCalc") )
+
     result.setPrivateTools( TileGeoG4SDTool(name, **kwargs)  )
     return result
 
@@ -23,7 +27,7 @@ def TileCTBGeoG4SDCfg(ConfigFlags, name="TileCTBGeoG4SD", **kwargs):
     kwargs.setdefault("LogicalVolumeNames", ["Tile::Scintillator"])
     kwargs.setdefault("OutputCollectionNames", ["TileHitVec"])
 
-    result = TileGeoG4SDCalcCfg(ConfigFlags)
+    result = TileCTBGeoG4SDCalcCfg(ConfigFlags)
     kwargs.setdefault("TileCalculator", result.getService("TileCTBGeoG4SDCalc") )
 
     result.setPrivateTools( TileGeoG4SDTool(name, **kwargs) )
diff --git a/Tools/FullChainTransforms/share/FastChainSkeleton.EVGENtoRDO.py b/Tools/FullChainTransforms/share/FastChainSkeleton.EVGENtoRDO.py
index 95c9dfcea82efc97fc3a814627e06e82ecb3cc58..6967fe25bc837d94634ec513a3f63773369b93f7 100644
--- a/Tools/FullChainTransforms/share/FastChainSkeleton.EVGENtoRDO.py
+++ b/Tools/FullChainTransforms/share/FastChainSkeleton.EVGENtoRDO.py
@@ -831,7 +831,7 @@ collection_merger_alg = CfgGetter.getAlgorithm('ISF_CollectionMerger')
 
 SimKernel = CfgGetter.getAlgorithm(ISF_Flags.Simulator.KernelName())
 
-if ISF_Flags.HITSMergingRequired():
+if ISF_Flags.HITSMergingRequired.anyOn():
     topSequence += collection_merger_alg
 
 #--------------------------------------------------------------