Index: firmware/App/Modes/ModeFill.c
===================================================================
diff -u -r83e2e219e3a8aeea65d6dbaeea15c9498427fd78 -r86617288c49b57eca42cf2d0b67ade76e69f96bd
--- firmware/App/Modes/ModeFill.c	(.../ModeFill.c)	(revision 83e2e219e3a8aeea65d6dbaeea15c9498427fd78)
+++ firmware/App/Modes/ModeFill.c	(.../ModeFill.c)	(revision 86617288c49b57eca42cf2d0b67ade76e69f96bd)
@@ -58,6 +58,8 @@
 #define MAXIMUM_DIALYSATE_TEMPERATURE                   42.0                                        ///< Maximum allowed dialysate temperature in degree C.
 #define MINIMUM_DIALYSATE_TEMPERATURE                   33.0                                        ///< Minimum allowed dialysate temperature in degree C.
 
+#define ONE_LITER_WEIGHT_GRAMS                          ( ML_PER_LITER )                            ///< One liter weight in grams.
+
 /// Multiplier to convert flow (L/min) into volume (mL) for period of general task interval.
 static const F32 RO_FLOW_INTEGRATOR = ( ( ML_PER_LITER * TASK_GENERAL_INTERVAL ) / ( SEC_PER_MIN * MS_PER_SECOND ) );
 
@@ -69,6 +71,8 @@
 static F32 totalROFlowRate_LPM;                         ///< Total RO flow rate over period of time.
 static U32 concentrateTestStartTime;                    ///< Starting time for concentrate test.
 static U32 waterQualityCheckStartTime;                  ///< Starting time for inlet water quality check.
+static F32 dialysateConductivityTotal;                  ///< Total of dialysate conductivity during fill.
+static U32 dialysateConductivitySampleCount;            ///< Sample count of dialysate conductivity during fill.
 
 // ********** private function prototypes **********
 
@@ -97,6 +101,8 @@
     reservoirBaseWeight = 0.0;
     totalROFlowRate_LPM = 0.0;
     concentrateTestStartTime = 0;
+    dialysateConductivityTotal = 0.0;
+    dialysateConductivitySampleCount = 0;
 
     initPersistentAlarm( ALARM_ID_ACID_CONDUCTIVITY_OUT_OF_RANGE, CONDUCTIVITY_ERROR_PERSISTENCE_PERIOD_MS, CONDUCTIVITY_ERROR_PERSISTENCE_PERIOD_MS );
     initPersistentAlarm( ALARM_ID_DIALYSATE_CONDUCTIVITY_OUT_OF_RANGE, CONDUCTIVITY_ERROR_PERSISTENCE_PERIOD_MS, CONDUCTIVITY_ERROR_PERSISTENCE_PERIOD_MS );
@@ -396,9 +402,12 @@
  *************************************************************************/
 static DG_FILL_MODE_STATE_T handleDeliverDialysateState( void )
 {
+    F32 avgDialysateConductivity;
     DG_FILL_MODE_STATE_T result = DG_FILL_MODE_STATE_DELIVER_DIALYSATE;
     DG_RESERVOIR_ID_T inactiveReservoir = getInactiveReservoir();
     totalROFlowRate_LPM += getMeasuredROFlowRate();
+    dialysateConductivityTotal += getConductivityValue( CONDUCTIVITYSENSORS_CD2_SENSOR );
+    dialysateConductivitySampleCount++;
 
     handleDialysateMixing();
 
@@ -410,6 +419,17 @@
 #endif
     }
 
+    if ( getReservoirWeight( inactiveReservoir ) >= ONE_LITER_WEIGHT_GRAMS )
+    {
+        avgDialysateConductivity = dialysateConductivityTotal / dialysateConductivitySampleCount;
+
+        if ( ( avgDialysateConductivity < MIN_DIALYSATE_CONDUCTIVITY ) || ( avgDialysateConductivity > MAX_DIALYSATE_CONDUCTIVITY ) )
+        {
+            SET_ALARM_WITH_1_F32_DATA( ALARM_ID_DIALYSATE_CONDUCTIVITY_FAULT, avgDialysateConductivity );
+            requestNewOperationMode( DG_MODE_CIRC );
+        }
+    }
+
     // if we've reached our target fill to volume (by weight), we're done filling - go back to re-circ mode
     if ( hasTargetFillVolumeBeenReached( inactiveReservoir ) )
     {