Index: firmware/App/Modes/ModeGenIdle.c
===================================================================
diff -u -r7d4711edd7b40cd3e29f43e766f79a8a09586fe9 -r9512e64a5eaf8206fae80473b1c98d6892010cde
--- firmware/App/Modes/ModeGenIdle.c	(.../ModeGenIdle.c)	(revision 7d4711edd7b40cd3e29f43e766f79a8a09586fe9)
+++ firmware/App/Modes/ModeGenIdle.c	(.../ModeGenIdle.c)	(revision 9512e64a5eaf8206fae80473b1c98d6892010cde)
@@ -47,6 +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 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.
@@ -66,6 +67,7 @@
 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.
 
 // ********** private function prototypes **********
 
@@ -140,6 +142,8 @@
 
     setCPLDCleanLEDColor( CPLD_CLEAN_LED_OFF );
 
+    initialReservoirWeight = getReservoirWeight( getInactiveReservoir() );
+
     return genIdleState;
 }
 
@@ -296,6 +300,7 @@
 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() );
 
     if ( ( TRUE == isAlarmActive( ALARM_ID_DG_ACID_BOTTLE_LOW_VOLUME ) ) || ( TRUE == isAlarmActive( ALARM_ID_DG_BICARB_BOTTLE_LOW_VOLUME ) ) )
     {
@@ -311,6 +316,12 @@
         startFillCmd( getTargetFillVolumeML(), getTargetFillFlowRateLPM() );
     }
 
+    // Check for unwanted filling
+    if ( reservoirWeight > ( initialReservoirWeight +  MAX_IDLE_RSVR_WEIGHT_GAIN ) )
+    {
+        SET_ALARM_WITH_1_U32_DATA( ALARM_ID_DG_INACTIVE_RESERVOIR_WEIGHT_OUT_OF_RANGE, reservoirWeight );
+    }
+
     return result;
 }