Index: firmware/App/Modes/ModeFill.c
===================================================================
diff -u -r2fafa5769ca6850277200ae0ec08a0e508b0d2ed -r4b15ae8df98dc7f3be2bd64984f2f53022c23fcd
--- firmware/App/Modes/ModeFill.c	(.../ModeFill.c)	(revision 2fafa5769ca6850277200ae0ec08a0e508b0d2ed)
+++ firmware/App/Modes/ModeFill.c	(.../ModeFill.c)	(revision 4b15ae8df98dc7f3be2bd64984f2f53022c23fcd)
@@ -54,7 +54,7 @@
 #define ACID_BICARB_CONCENTRATE_ADDITION_MULTIPLER      1.06                                        ///< Acid and bicarbonate concentrates make up around 6% to total volume.
 #define FLOW_INTEGRATED_VOLUME_CHECK_TOLERANCE          0.1                                         ///< Flow integrated volume has 10% tolerance compare to load cell reading.
 
-#define CONCENTRATE_TEST_TIME_OUT_MS                    ( SEC_PER_MIN * MS_PER_SECOND )             ///< Concentrate test time out period in ms.
+#define CONCENTRATE_TEST_TIME_OUT_MS                    ( 30 * MS_PER_SECOND )                      ///< Concentrate test time out period in ms.
 #define WATER_QUALITY_CHECK_TIME_OUT_MS                 ( 30 * MS_PER_SECOND )                      ///< Inlet water quality check time out period in ms.
 
 #define CONDUCTIVITY_ERROR_PERSISTENCE_PERIOD_MS        ( 15 * MS_PER_SECOND )                      ///< Persistence period for conductivity error.
@@ -78,6 +78,7 @@
 static F32 dialysateConductivityTotal;                  ///< Total of dialysate conductivity during fill.
 static U32 dialysateConductivitySampleCount;            ///< Sample count of dialysate conductivity during fill.
 static U32 concentratePumpTestPersistentCount;          ///< Persistent count for concentrate pump testing.
+static U32 concentratePumpPrimeCount;
 
 // ********** private function prototypes **********
 
@@ -110,6 +111,7 @@
     dialysateConductivityTotal = 0.0;
     dialysateConductivitySampleCount = 0;
     concentratePumpTestPersistentCount = 0;
+    concentratePumpPrimeCount = 0;
 
     initPersistentAlarm( ALARM_ID_DIALYSATE_CONDUCTIVITY_OUT_OF_RANGE, CONDUCTIVITY_CLEAR_PERSISTENCE_PERIOD_MS, CONDUCTIVITY_ERROR_PERSISTENCE_PERIOD_MS );
 }
@@ -235,11 +237,12 @@
 static BOOL checkDialysateConductivity( void )
 {
     BOOL const isDialysateConductivityGood = isDialysateConductivityInRange();
+    F32 const acidConductivity = getConductivityValue( CONDUCTIVITYSENSORS_CD1_SENSOR );
 
     if ( TRUE == isPersistentAlarmTriggered( ALARM_ID_DIALYSATE_CONDUCTIVITY_OUT_OF_RANGE, !isDialysateConductivityGood ) )
     {
 #ifndef DISABLE_DIALYSATE_CHECK
-        if ( FALSE == isAcidConductivityInRange() )
+        if ( ( MIN_ACID_CONCENTRATE_CONDUCTIVITY <= acidConductivity ) && ( acidConductivity <= MAX_ACID_CONCENTRATE_CONDUCTIVITY ) )
         {
             SET_ALARM_WITH_1_F32_DATA( ALARM_ID_ACID_CONDUCTIVITY_OUT_OF_RANGE, getConductivityValue( CONDUCTIVITYSENSORS_CD1_SENSOR ) );
         }
@@ -296,6 +299,7 @@
         concentrateTestStartTime = getMSTimerCount();
         requestConcentratePumpsOff( CONCENTRATEPUMPS_CP1_ACID );
         requestConcentratePumpsOn( CONCENTRATEPUMPS_CP2_BICARB );
+        setConcentratePumpTargetSpeed( CONCENTRATEPUMPS_CP2_BICARB, 40.0 );
         result = DG_FILL_MODE_STATE_BICARB_PUMP_CHECK;
     }
 
@@ -319,21 +323,37 @@
 static DG_FILL_MODE_STATE_T handleBicarbPumpCheckState( void )
 {
     DG_FILL_MODE_STATE_T result = DG_FILL_MODE_STATE_BICARB_PUMP_CHECK;
+    F32 const bicarbConductivity = getConductivityValue( CONDUCTIVITYSENSORS_CD2_SENSOR );
 
-    handleDialysateMixing();
+    if ( MIN_BICARB_CONCENTRATE_CONDUCTIVITY <= bicarbConductivity )
+    {
+        if ( concentratePumpPrimeCount++ > CONCENTRATE_PUMP_PRIME_INTERVAL )
+        {
+            F32 const measuredROFlowRate = getMeasuredROFlowRate();
+            F32 const bicarbCP2PumpFlowRate = DIALYSATE_BICARB_CONCENTRATE_RATIO * measuredROFlowRate * ML_PER_LITER;
 
+            setConcentratePumpTargetSpeed( CONCENTRATEPUMPS_CP2_BICARB, bicarbCP2PumpFlowRate );
+        }
+    }
+    else
+    {
+        concentratePumpPrimeCount = 0;
+    }
+
 #ifndef DISABLE_DIALYSATE_CHECK
-    if ( TRUE == isBicarbConductivityInRange() )
+    if ( ( MIN_BICARB_CONCENTRATE_CONDUCTIVITY <= bicarbConductivity ) && ( bicarbConductivity <= MAX_BICARB_CONCENTRATE_CONDUCTIVITY ) )
 #else
     if ( TRUE )
 #endif
     {
         if ( concentratePumpTestPersistentCount++ > CONCENTRATE_PUMP_TEST_PERSISTENT_INTERVAL )
         {
             concentratePumpTestPersistentCount = 0;
+            concentratePumpPrimeCount = 0;
             concentrateTestStartTime = getMSTimerCount();
             requestConcentratePumpsOn( CONCENTRATEPUMPS_CP1_ACID );
             requestConcentratePumpsOff( CONCENTRATEPUMPS_CP2_BICARB );
+            setConcentratePumpTargetSpeed( CONCENTRATEPUMPS_CP1_ACID, 40.0 );
             result = DG_FILL_MODE_STATE_ACID_PUMP_CHECK;
         }
     }
@@ -362,11 +382,25 @@
 static DG_FILL_MODE_STATE_T handleAcidPumpCheckState( void )
 {
     DG_FILL_MODE_STATE_T result = DG_FILL_MODE_STATE_ACID_PUMP_CHECK;
+    F32 const acidConductivity = getConductivityValue( CONDUCTIVITYSENSORS_CD1_SENSOR );
 
-    handleDialysateMixing();
+    if ( MIN_ACID_CONCENTRATE_CONDUCTIVITY <= acidConductivity )
+    {
+        if ( concentratePumpPrimeCount++ > CONCENTRATE_PUMP_PRIME_INTERVAL )
+        {
+            F32 const measuredROFlowRate = getMeasuredROFlowRate();
+            F32 const acidCP1PumpFlowRate = DIALYSATE_ACID_CONCENTRATE_RATIO * measuredROFlowRate * ML_PER_LITER;
 
+            setConcentratePumpTargetSpeed( CONCENTRATEPUMPS_CP1_ACID, acidCP1PumpFlowRate );
+        }
+    }
+    else
+    {
+        concentratePumpPrimeCount = 0;
+    }
+
 #ifndef DISABLE_DIALYSATE_CHECK
-    if ( TRUE == isAcidConductivityInRange() )
+    if ( ( MIN_ACID_CONCENTRATE_CONDUCTIVITY <= acidConductivity ) && ( acidConductivity <= MAX_ACID_CONCENTRATE_CONDUCTIVITY ) )
 #else
     if ( TRUE )
 #endif