Index: firmware/App/Modes/ModeGenIdle.c
===================================================================
diff -u -r137f0bcce332075c1aade79b52c572a095934775 -r42128f305793acaf5f4387ec1825281911d62bff
--- firmware/App/Modes/ModeGenIdle.c	(.../ModeGenIdle.c)	(revision 137f0bcce332075c1aade79b52c572a095934775)
+++ firmware/App/Modes/ModeGenIdle.c	(.../ModeGenIdle.c)	(revision 42128f305793acaf5f4387ec1825281911d62bff)
@@ -47,7 +47,7 @@
 
 #define TARGET_RO_PRESSURE_PSI                  130                                            ///< Target pressure for RO pump.
 #define TARGET_RO_FLOW_RATE_L                   0.8F                                           ///< Target flow rate for RO pump.
-#define MAX_IDLE_RSVR_WEIGHT_GAIN               200.0F                                         ///< Maximum mL gain of inactive reservoir in Gen Idle mode
+#define MAX_IDLE_RSVR_WEIGHT_GAIN_ML            200.0F                                         ///< Maximum fluid gain of inactive reservoir in Gen Idle mode (mL)
 #define HD_LOST_COMM_TIMEOUT_MS                 (5 * SEC_PER_MIN * MS_PER_SECOND )             ///< The time of HD lost comm before DG transition back to standby.
 #define BAD_FILL_SUBSTATES_PUB_INTERVAL         ( MS_PER_SECOND / TASK_GENERAL_INTERVAL )      ///< Interval (ms/task time) at which the bad fill sub-states is published on the CAN bus.
 #define DATA_PUBLISH_COUNTER_START_COUNT        61                                             ///< Data publish counter start count.
@@ -67,7 +67,8 @@
 static OVERRIDE_U32_T genIdleDataPublicationInterval = { BAD_FILL_SUBSTATES_PUB_INTERVAL,
                                                          BAD_FILL_SUBSTATES_PUB_INTERVAL,
                                                          0, 0 };                               ///< Interval (in ms) at which to publish bad fill sub-states to CAN bus.
-static F32 initialReservoirWeight;                                                             ///< Initial weight of incative reservoir in Gen Idle mode.
+static F32 initialReservoirWeight;                                                             ///< Initial weight of inactive reservoir in Gen Idle mode.
+static DG_RESERVOIR_ID_T inactiveReservoir;                                                    ///< Inactive reservoir
 
 // ********** private function prototypes **********
 
@@ -142,7 +143,8 @@
 
     setCPLDCleanLEDColor( CPLD_CLEAN_LED_OFF );
 
-    initialReservoirWeight = getReservoirWeight( getInactiveReservoir() );
+    inactiveReservoir = getInactiveReservoir();
+    initialReservoirWeight = getReservoirWeight( inactiveReservoir );
 
     return genIdleState;
 }
@@ -300,7 +302,8 @@
 static DG_GEN_IDLE_MODE_STATE_T handleFlushWaterState( void )
 {
     DG_GEN_IDLE_MODE_STATE_T result = DG_GEN_IDLE_MODE_STATE_FLUSH_WATER;
-    F32 reservoirWeight = getReservoirWeight( getInactiveReservoir() );
+    DG_RESERVOIR_ID_T currentInactiveReservoir = getInactiveReservoir();
+    F32 reservoirWeight = getReservoirWeight( currentInactiveReservoir );
 
     if ( ( TRUE == isAlarmActive( ALARM_ID_DG_ACID_BOTTLE_LOW_VOLUME ) ) || ( TRUE == isAlarmActive( ALARM_ID_DG_BICARB_BOTTLE_LOW_VOLUME ) ) )
     {
@@ -316,10 +319,17 @@
         startFillCmd( getTargetFillVolumeML(), getTargetFillFlowRateLPM() );
     }
 
+    if ( currentInactiveReservoir != inactiveReservoir )
+    {
+        // Inactive Reservoir changed, update the start value
+        inactiveReservoir = currentInactiveReservoir;
+        initialReservoirWeight = getReservoirWeight( inactiveReservoir );
+    }
+
     // Check for unwanted filling
-    if ( reservoirWeight > ( initialReservoirWeight +  MAX_IDLE_RSVR_WEIGHT_GAIN ) )
+    if ( reservoirWeight > ( initialReservoirWeight +  MAX_IDLE_RSVR_WEIGHT_GAIN_ML ) )
     {
-        SET_ALARM_WITH_1_U32_DATA( ALARM_ID_DG_INACTIVE_RESERVOIR_WEIGHT_OUT_OF_RANGE, reservoirWeight );
+        SET_ALARM_WITH_2_U32_DATA( ALARM_ID_DG_INACTIVE_RESERVOIR_WEIGHT_OUT_OF_RANGE, initialReservoirWeight, reservoirWeight );
     }
 
     return result;