Index: firmware/App/Controllers/ConcentratePumps.c
===================================================================
diff -u -r3f22d883958a14b6193d6cd59c9acdbbd359b69e -rd717fd8e877c00b205621ca5ef885c9a59c47376
--- firmware/App/Controllers/ConcentratePumps.c	(.../ConcentratePumps.c)	(revision 3f22d883958a14b6193d6cd59c9acdbbd359b69e)
+++ firmware/App/Controllers/ConcentratePumps.c	(.../ConcentratePumps.c)	(revision d717fd8e877c00b205621ca5ef885c9a59c47376)
@@ -36,7 +36,7 @@
 #define CONCENTRATE_PUMP_MIN_SPEED                          3.0                                                 ///< Minimum speed for concentrate pump in mL per min.
 #define CONCENTRATE_PUMP_MAX_SPEED                          49.0                                                ///< Maximum speed for concentrate pump in mL per min.
 #define CONCENTRATE_PUMP_ERROR_TOLERANCE                    0.02                                                ///< Measured speed needs to be within 2% of commanded speed.
-#define CONCENTRATE_PUMP_ZERO_FLOW_RATE_PULSE_WIDTH         0xFFFF                                              ///< Pulse width value when zero flow rate or pump is off.
+#define CONCENTRATE_PUMP_ZERO_FLOW_RATE                     0xFFFF                                              ///< Pulse width value when zero flow rate or pump is off.
 
 #define CONCENTRATE_PUMP_VOLUME_PER_REV                     0.15                                                ///< Volume output every revolution (mL).
 #define CONCENTRATE_PUMP_PULSE_PER_REV                      4.0                                                 ///< Number of pulses generate for every revolution.
@@ -64,8 +64,7 @@
 // ********** private data **********
 
 static CONCENTRATE_PUMP_STATE_T concentratePumpState;                   ///< Concentrate pump module current state.
-static BOOL isPumpOnRequested;                                          ///< Flag indicates a request to turn concentrate pumps on.
-static BOOL isPumpOffRequested;                                         ///< Flag indicates a request to turn concentrate pumps off.
+static BOOL hasTurnOnPumpsBeenRequested;                                ///< Flag indicates a request to turn concentrate pumps on.
 static U32 concentratePumpControlTimerCounter;                          ///< Timer counter to perform control on concentrate pump.
 static U32 concentratePumpMonitorTimerCounter;                          ///< Timer counter to perform monitor on concentrate pump.
 
@@ -99,8 +98,7 @@
 void initConcentratePump( void )
 {
     concentratePumpState = CONCENTRATE_PUMP_OFF_STATE;
-    isPumpOnRequested    = FALSE;
-    isPumpOffRequested   = FALSE;
+    hasTurnOnPumpsBeenRequested = FALSE;
     concentratePumpControlTimerCounter = 0;
     concentratePumpMonitorTimerCounter = 0;
 
@@ -180,7 +178,7 @@
  *************************************************************************/
 void requestConcentratePumpsOn( void )
 {
-    isPumpOnRequested = TRUE;
+    hasTurnOnPumpsBeenRequested = TRUE;
 }
 
 /*********************************************************************//**
@@ -193,7 +191,7 @@
  *************************************************************************/
 void requestConcentratePumpsOff( void )
 {
-    isPumpOffRequested = TRUE;
+    hasTurnOnPumpsBeenRequested = FALSE;
     pumpTargetSpeed[ CONCENTRATEPUMPS_CP1 ] = 0.0;
     pumpTargetSpeed[ CONCENTRATEPUMPS_CP2 ] = 0.0;
 }
@@ -264,13 +262,12 @@
 {
     CONCENTRATE_PUMP_STATE_T state = CONCENTRATE_PUMP_OFF_STATE;
 
-    if ( isPumpOnRequested )
+    if ( TRUE == hasTurnOnPumpsBeenRequested )
     {
         setFPGACP1Control( CONCENTRATE_PUMP_ON_CONTROL );
         setFPGACP2Control( CONCENTRATE_PUMP_ON_CONTROL );
 
         state = CONCENTRATE_PUMP_ON_STATE;
-        isPumpOnRequested = FALSE;
     }
 
     return state;
@@ -310,9 +307,16 @@
         currentPumpSpeed[ pumpId ] += speedIncrease;
     }
 
-    F32 const timePerStep = CONCENTRATE_PUMP_VOLUME_PER_REV / ( currentPumpSpeed[ pumpId ] * CONCENTRATE_PUMP_STEP_PER_REV ) ;
-    F32 const stepPeriodCounts = timePerStep / ( CONCENTRATE_PUMP_STEP_PERIOD_RESOLUTION * CONCENTRATE_PUMP_MICRO_STEPS_PER_STEP );
-    togglePeriodCount[ pumpId ] = (U16)( stepPeriodCounts + 0.5 );
+    if ( currentPumpSpeed[ pumpId ] > NEARLY_ZERO )
+    {
+        F32 const timePerStep = CONCENTRATE_PUMP_VOLUME_PER_REV / ( currentPumpSpeed[ pumpId ] * CONCENTRATE_PUMP_STEP_PER_REV ) ;
+        F32 const stepPeriodCounts = timePerStep / ( CONCENTRATE_PUMP_STEP_PERIOD_RESOLUTION * CONCENTRATE_PUMP_MICRO_STEPS_PER_STEP );
+        togglePeriodCount[ pumpId ] = (U16)( stepPeriodCounts + 0.5 );
+    }
+    else
+    {
+        togglePeriodCount[ pumpId ] = CONCENTRATE_PUMP_ZERO_FLOW_RATE;
+    }
 }
 
 /*********************************************************************//**
@@ -339,11 +343,9 @@
         setFPGACP2SetStepSpeed( togglePeriodCount[ CONCENTRATEPUMPS_CP2 ] );
     }
 
-    if ( isPumpOffRequested )
+    if ( FALSE == hasTurnOnPumpsBeenRequested )
     {
         state = CONCENTRATE_PUMP_OFF_STATE;
-        isPumpOffRequested = FALSE;
-
         stopConcentratePump();
     }
 
@@ -385,7 +387,7 @@
     F32 const pulseWidthInSecond = (F32)( pulseWidthCount * CONCENTRATE_PUMP_HALL_SENSE_PERIOD_RESOLUTION ) / US_PER_SECOND;
     measuredPumpSpeed[ pumpId ].data = ( 1 / pulseWidthInSecond ) * CONCENTRATE_PUMP_VOLUME_PER_PULSE * SEC_PER_MIN;
 
-    if ( CONCENTRATE_PUMP_ZERO_FLOW_RATE_PULSE_WIDTH == pulseWidthCount )
+    if ( CONCENTRATE_PUMP_ZERO_FLOW_RATE == pulseWidthCount )
     {
         measuredPumpSpeed[ pumpId ].data = 0.0;
     }