Index: firmware/App/Modes/ModeDrain.c
===================================================================
diff -u -r7d4711edd7b40cd3e29f43e766f79a8a09586fe9 -r18a83ba64d9560ce8c4c009560ec1391ae15102f
--- firmware/App/Modes/ModeDrain.c	(.../ModeDrain.c)	(revision 7d4711edd7b40cd3e29f43e766f79a8a09586fe9)
+++ firmware/App/Modes/ModeDrain.c	(.../ModeDrain.c)	(revision 18a83ba64d9560ce8c4c009560ec1391ae15102f)
@@ -66,15 +66,8 @@
 #define ACID_PERCENT_FILL                        0.02222F                                              ///< Acid volume percentage of reservoir volume.
 #define DATA_PUBLISH_COUNTER_START_COUNT         70                                                    ///< Data publish counter start count.
 #define DRAIN_MODE_DATA_PUB_INTERVAL             ( MS_PER_SECOND / TASK_GENERAL_INTERVAL )             ///< Interval (ms/task time) at which the drain mode data is published on the CAN bus.
+#define MIN_CONCENTRATE_VOLUME_ML                500.0F                                                ///< Minimum concentrate volume in milliliters.
 
-///< Concentrate bottle acid low volume in mL.
-static const F32 CONCENTRATE_BOTTLE_ACID_LOW_VOLUME_ML   = ( CONCENTRATE_BOTTLE_PRIMING_VOL_ML +
-                                                             ( CONCENTRATE_BOTTLE_RESERVOIOR_VOL_ML * CONCENTRATE_BOTTLE_RESERVOIOR_FILLS * ACID_PERCENT_FILL) );
-
-///< Concentrate bottle bicarb low volume in mL.
-static const F32 CONCENTRATE_BOTTLE_BICARB_LOW_VOLUME_ML = ( CONCENTRATE_BOTTLE_PRIMING_VOL_ML +
-                                                             ( CONCENTRATE_BOTTLE_RESERVOIOR_VOL_ML * CONCENTRATE_BOTTLE_RESERVOIOR_FILLS * BICARB_PERCENT_FILL) );
-
 // ********** private data **********
 
 static DG_DRAIN_STATE_T drainState;                                                                    ///< Currently active drain state.
@@ -313,7 +306,7 @@
             getHDOperationMode( &hdMode );
 
             // Detect empty bottles using integrated volumes
-            if ( ( ( acidBottleVolML - getChemicalUsedVolumeML( ACID ) ) <= CONCENTRATE_BOTTLE_ACID_LOW_VOLUME_ML ) && // SRSDG 836
+            if ( ( ( acidBottleVolML - getChemicalUsedVolumeML( ACID ) ) <= MIN_CONCENTRATE_VOLUME_ML ) && // SRSDG 836
                  ( hdMode.hdMode != MODE_POST ) &&                            // don't care about concentrates after treatment complete
                  ( getTestConfigStatus( TEST_CONFIG_MIX_WITH_WATER ) != TRUE ) )
             {
@@ -323,7 +316,7 @@
                 activateAlarmNoData ( ALARM_ID_DG_CREATING_DIALYSATE_PLEASE_WAIT );
             }
 
-            if ( ( ( bicarbBottleVolML - getChemicalUsedVolumeML( BICARB ) ) <= CONCENTRATE_BOTTLE_BICARB_LOW_VOLUME_ML ) &&  // SRSDG 837
+            if ( ( ( bicarbBottleVolML - getChemicalUsedVolumeML( BICARB ) ) <= MIN_CONCENTRATE_VOLUME_ML ) &&  // SRSDG 837
                  ( hdMode.hdMode != MODE_POST ) &&                            // don't care about concentrates after treatment complete
                  ( getTestConfigStatus( TEST_CONFIG_MIX_WITH_WATER ) != TRUE ) )
             {
Index: firmware/App/Modes/ModeFill.c
===================================================================
diff -u -ra7236428780daa67552e2b1e0b4b05a4f1ffbe82 -r18a83ba64d9560ce8c4c009560ec1391ae15102f
--- firmware/App/Modes/ModeFill.c	(.../ModeFill.c)	(revision a7236428780daa67552e2b1e0b4b05a4f1ffbe82)
+++ firmware/App/Modes/ModeFill.c	(.../ModeFill.c)	(revision 18a83ba64d9560ce8c4c009560ec1391ae15102f)
@@ -194,6 +194,7 @@
 static void handleDialysateMixing( F32 measuredROFlowRate_mL_min, F32 acidMixingRatio, F32 bicarbMixingRatio );
 static BOOL isValueWithinPercentRange( F32 testValue, F32 baseValue, F32 percentFactor );
 static void publishFillModeData( void );
+static void updateChemicalsUsage( void );
 
 /*********************************************************************//**
  * @brief
@@ -352,6 +353,7 @@
 {
     checkDialysateTemperatureSensors();
     setHeaterTargetTemperature( DG_PRIMARY_HEATER, getPrimaryHeaterTargetTemperature() );
+    updateChemicalsUsage();
 
     if ( fillState != DG_FILL_MODE_STATE_PAUSED )
     {
@@ -623,8 +625,6 @@
         // to dialysate production directly
         if ( TRUE == isThisTheFirstFill() )
         {
-            resetChemicalUsedVolumeML( BICARB );
-            resetChemicalUsedVolumeML( ACID );
             result = DG_FILL_MODE_STATE_PRIME_CONCENTRATE_LINES;
         }
         else
@@ -922,8 +922,6 @@
         integratedVolumeML.data += getMeasuredROFlowRateWithConcPumpsLPM() * ML_PER_LITER * FLOW_INTEGRATOR;
     }
 
-    usedAcidVolumeML.data   += getMeasuredPumpSpeedMLPM( CONCENTRATEPUMPS_CP1_ACID ) * FLOW_INTEGRATOR;
-    usedBicarbVolumeML.data += getMeasuredPumpSpeedMLPM( CONCENTRATEPUMPS_CP2_BICARB ) * FLOW_INTEGRATOR;
     acidConductivityTotal   += acidConduSPerCM;
     bicarbConductivityTotal += bicarbConduSPerCM;
     conductivitySampleCount++;
@@ -1319,7 +1317,20 @@
     }
 }
 
+/*********************************************************************//**
+ * @brief
+ * The updateChemicalsUsage function updates the used acid and bicarb volumes.
+ * @details Inputs: usedAcidVolumeML, usedBicarbVolumeML
+ * @details Outputs: none
+ * @return none
+ *************************************************************************/
+static void updateChemicalsUsage( void )
+{
+    usedAcidVolumeML.data   += getMeasuredPumpSpeedMLPM( CONCENTRATEPUMPS_CP1_ACID ) * FLOW_INTEGRATOR;
+    usedBicarbVolumeML.data += getMeasuredPumpSpeedMLPM( CONCENTRATEPUMPS_CP2_BICARB ) * FLOW_INTEGRATOR;
+}
 
+
 /*************************************************************************
  *                       TEST SUPPORT FUNCTIONS
  *************************************************************************/
Index: firmware/App/Modes/ModeStandby.c
===================================================================
diff -u -re6c60e07b450ec8d58e87bf13d45f96efab54d8b -r18a83ba64d9560ce8c4c009560ec1391ae15102f
--- firmware/App/Modes/ModeStandby.c	(.../ModeStandby.c)	(revision e6c60e07b450ec8d58e87bf13d45f96efab54d8b)
+++ firmware/App/Modes/ModeStandby.c	(.../ModeStandby.c)	(revision 18a83ba64d9560ce8c4c009560ec1391ae15102f)
@@ -23,6 +23,7 @@
 #include "MessageSupport.h"
 #include "ModeChemicalDisinfect.h"
 #include "ModeFault.h"
+#include "ModeFill.h"
 #include "ModeHeatDisinfect.h"
 #include "ModeStandby.h"
 #include "NVDataMgmt.h"
@@ -263,6 +264,9 @@
     {
         pendingStartDGRequest = FALSE;
         signalSyncToHD();
+        // About to start a treatment reset the chemical bottles volumes (regardless whether the user has inserted new bottles)
+        resetChemicalUsedVolumeML( BICARB );
+        resetChemicalUsedVolumeML( ACID );
         requestNewOperationMode( DG_MODE_GENE );
     }
     else if ( TRUE == pendingStartDGFlushRequest )