Index: firmware/App/Modes/Dialysis.c
===================================================================
diff -u -rbac52336ea9e23fc2dfb4a802afe49401dfb7057 -r00ff72e0b1cf3002e660d850346e26e1209e2b24
--- firmware/App/Modes/Dialysis.c	(.../Dialysis.c)	(revision bac52336ea9e23fc2dfb4a802afe49401dfb7057)
+++ firmware/App/Modes/Dialysis.c	(.../Dialysis.c)	(revision 00ff72e0b1cf3002e660d850346e26e1209e2b24)
@@ -71,6 +71,7 @@
     F32 DPiToBLDFlushedVolML;                                ///< Dialysate inlet pump to blood leak flushed volume in milliliters.
     BOOL hasBloodLeakZeroingBeenRequested;                   ///< Flag to indicate blood leak zeroing has been requested.
     BOOL isZeroingRequestedFromTreatmentStop;                ///< Flag to indicate blood leak zeroing has been requested from treatment stop.
+    BOOL isZeroingNeededAfterRsrvrSwitch;                    ///< Flag to indicate blood leak zeroing is needed after reservoir switch.
     BLOOD_LEAK_ZEROING_STATE_T bloodLeakZeroingState;        ///< Blood leak zeroing state.
 } BLOOD_LEAK_ZEROING_T ;
 
@@ -694,13 +695,23 @@
     // Check ultrafiltration control during dialysis (even when ultrafiltration is paused).
     checkUFControl();
 
-    if ( ( TRUE == isBloodLeakZeroingNeeded() ) && ( DIALYSIS_UF_STATE == currentDialysisState ) )
+    if ( TRUE == isBloodLeakZeroingNeeded() )
     {
-        // Reset the blood leak zeroing variables
-        resetBloodLeakZeroing();
-        requestBloodLeakZeroing( FALSE );
+        bloodLeakZeroingStatus.isZeroingNeededAfterRsrvrSwitch = TRUE;
     }
 
+    if ( ( TRUE == bloodLeakZeroingStatus.isZeroingNeededAfterRsrvrSwitch ) && ( DIALYSIS_UF_STATE == currentDialysisState ) )
+    {
+        if ( TRUE == checkReservoirHasBeenSwitched() )
+        {
+            // Reset the blood leak zeroing variables
+            resetBloodLeakZeroing();
+            requestBloodLeakZeroing( FALSE );
+        }
+    }
+
+    resetReservoirSwitchFlag();
+
     // Dialysis state machine
     switch ( currentDialysisState )
     {
@@ -1545,6 +1556,7 @@
     bloodLeakZeroingStatus.bloodLeakZeroingState               = BLD_ZEROING_IDLE_STATE;
     bloodLeakZeroingStatus.hasBloodLeakZeroingBeenRequested    = FALSE;
     bloodLeakZeroingStatus.isZeroingRequestedFromTreatmentStop = FALSE;
+    bloodLeakZeroingStatus.isZeroingNeededAfterRsrvrSwitch     = FALSE;
 }
 
 /*********************************************************************//**
Index: firmware/App/Modes/ModePreTreat.c
===================================================================
diff -u -rbac52336ea9e23fc2dfb4a802afe49401dfb7057 -r00ff72e0b1cf3002e660d850346e26e1209e2b24
--- firmware/App/Modes/ModePreTreat.c	(.../ModePreTreat.c)	(revision bac52336ea9e23fc2dfb4a802afe49401dfb7057)
+++ firmware/App/Modes/ModePreTreat.c	(.../ModePreTreat.c)	(revision 00ff72e0b1cf3002e660d850346e26e1209e2b24)
@@ -1178,6 +1178,7 @@
 
         if ( TRUE == isBloodLeakZeroingNeeded() )
         {
+            // If the sensor has drifted request a zero prior to transitioning to treatment
             zeroBloodLeak();
         }
 
Index: firmware/App/Services/Reservoirs.c
===================================================================
diff -u -ra36a3feca5d35137f1db0293882af0f49ebb9f03 -r00ff72e0b1cf3002e660d850346e26e1209e2b24
--- firmware/App/Services/Reservoirs.c	(.../Reservoirs.c)	(revision a36a3feca5d35137f1db0293882af0f49ebb9f03)
+++ firmware/App/Services/Reservoirs.c	(.../Reservoirs.c)	(revision 00ff72e0b1cf3002e660d850346e26e1209e2b24)
@@ -96,6 +96,7 @@
 static F32 previousUFFlowMLP;                                                                            ///< Previous ultrafiltration flow rate in mL/min.
 static DG_MIXING_RATIOS_T ratios;                                                                        ///< Mixing ratios and fill prep time in milliseconds structure.
 static U32 prevTargetFillVolumeML[ NUM_OF_DG_RESERVOIRS ];                                               ///< Previous target fill volume in milliliters.
+static BOOL hasReservoirBeenSwitched;                                                                    ///< Flag to indicate reservoir has been recently switched.
 
 static const F32 RESERVOIR_DILUTION_RATIO = MAX_RESERVOIR_DILUTION / ( 1.0 - MAX_RESERVOIR_DILUTION );   ///< Reservoir dilution ratio.
 
@@ -127,7 +128,7 @@
  * volSpentMl, reservoirsPublicationCounter, dilutionLevelPct, dgOpMode, dgSubMode,
  * timeReservoirInUse, volSpentUFML, activeReservoir, recirculationLevelPct,
  * reservoirSwitchStartTimeMS, timeWaitToFillMS, targetFillFlowLPM, ratios
- * previousDialysateFlowRate, prevTargetFillVolumeML
+ * previousDialysateFlowRate, prevTargetFillVolumeML, hasReservoirBeenSwitched
  * @return none
  *************************************************************************/
 void initReservoirs( void )
@@ -155,6 +156,7 @@
     ratios.acidMixingRatio      = 0.0F;
     ratios.bicarbMixingRatio    = 0.0F;
     ratios.timeFillPrepMS       = 0;
+    hasReservoirBeenSwitched    = FALSE;
 
     // Initialize the previous reservoir fill volume
     prevTargetFillVolumeML[ DG_RESERVOIR_1 ] = FILL_RESERVOIR_TO_VOLUME_ML;
@@ -270,6 +272,32 @@
     timeReservoirInUF += TASK_GENERAL_INTERVAL;
 }
 
+/*********************************************************************//**
+ * @brief
+ * The checkReservoirHasBeenSwitched function returns the reservoir has been
+ * switched flag.
+ * @details Inputs: none
+ * @details Outputs: hasReservoirBeenSwitched
+ * @return reservoir has been switched flag
+ *************************************************************************/
+BOOL checkReservoirHasBeenSwitched( void )
+{
+    return hasReservoirBeenSwitched;
+}
+
+/*********************************************************************//**
+ * @brief
+ * The resetReservoirSwitchFlag function resets the reservoir has been
+ * switched flag.
+ * @details Inputs: none
+ * @details Outputs: hasReservoirBeenSwitched
+ * @return none
+ *************************************************************************/
+void resetReservoirSwitchFlag( void )
+{
+    hasReservoirBeenSwitched = FALSE;
+}
+
 // ********** private functions **********
 
 /*********************************************************************//**
@@ -675,7 +703,8 @@
  * The handleReservoirMgmtWaitForSwitchSettleState function executes the reservoir
  * management wait for switch to settle state.
  * @details Inputs: reservoirSwitchStartTimeMS
- * @details Outputs: timeReservoirInUse
+ * @details Outputs: timeReservoirInUse, lastTimeReservoirInUF, timeReservoirInUF
+ * hasReservoirBeenSwitched
  * @return next reservoir management state of the state machine
  *************************************************************************/
 static TREATMENT_RESERVOIR_MGMT_STATE_T handleReservoirMgmtWaitForSwitchSettleState( void )
@@ -685,9 +714,10 @@
     if ( TRUE == didTimeout( reservoirSwitchStartTimeMS, RESERVOIR_USED_SETTLE_TIME_MS ) )
     {
         // Switching the active reservoir so reset the reservoir in use timer
-        lastTimeReservoirInUF = timeReservoirInUF;
-        timeReservoirInUF = 0;
-        timeReservoirInUse = 0;
+        lastTimeReservoirInUF    = timeReservoirInUF;
+        timeReservoirInUF        = 0;
+        timeReservoirInUse       = 0;
+        hasReservoirBeenSwitched = TRUE;
 
         // Signal dialysis sub-mode to capture final volume of prior reservoir after settling.
         setFinalReservoirVolume();
Index: firmware/App/Services/Reservoirs.h
===================================================================
diff -u -r20d0c02f453b6dae1884fb1b5ba542053852ffc1 -r00ff72e0b1cf3002e660d850346e26e1209e2b24
--- firmware/App/Services/Reservoirs.h	(.../Reservoirs.h)	(revision 20d0c02f453b6dae1884fb1b5ba542053852ffc1)
+++ firmware/App/Services/Reservoirs.h	(.../Reservoirs.h)	(revision 00ff72e0b1cf3002e660d850346e26e1209e2b24)
@@ -56,6 +56,9 @@
 
 void updateReservoirUFTime( void );                     // Update time spent doing ultrafiltration for currently active reservoir
 U32  getLastReservoirUFTimeInMs( void );                // Get the time spent doing ultrafiltration on the previously active reservoir
+BOOL checkReservoirHasBeenSwitched( void );
+void resetReservoirSwitchFlag( void );
+
 BOOL testSetRecirculationLevelPctOverride( F32 value ); // Set override for reciruclation percentage
 BOOL testResetRecirculationLevelPctOverride( void );    // Reset override for recirulation percentage
 /**@}*/