Index: firmware/App/Modes/ModeStandby.c
===================================================================
diff -u -rd325999b7b3ea03b7e294cb8a0b97df93812fbe9 -r79b494c344417ba6865db01ad5f456e439bec1b2
--- firmware/App/Modes/ModeStandby.c	(.../ModeStandby.c)	(revision d325999b7b3ea03b7e294cb8a0b97df93812fbe9)
+++ firmware/App/Modes/ModeStandby.c	(.../ModeStandby.c)	(revision 79b494c344417ba6865db01ad5f456e439bec1b2)
@@ -497,6 +497,29 @@
 
 /*********************************************************************//**
  * @brief
+ * The signalAbortWaterSampling function handles an HD request to abort water
+ * sampling (return to standby idle state).
+ * @details Inputs: none
+ * @details Outputs: standby mode variable initialized
+ * @return TRUE if request accepted, FALSE if not
+ *************************************************************************/
+BOOL signalAbortWaterSampling( void )
+{
+    BOOL result = FALSE;
+
+    if ( ( DG_MODE_STAN == getCurrentOperationMode() ) && ( standbyState != DG_STANDBY_MODE_STATE_IDLE ) )
+    {
+        result = TRUE;
+        initStandbyMode();
+        setValveState( VSP, VALVE_STATE_CLOSED );
+        setValveState( VPI, VALVE_STATE_CLOSED );
+    }
+
+    return result;
+}
+
+/*********************************************************************//**
+ * @brief
  * The startDGFlush function starts DG flush mode.
  * @details Inputs: standbyState
  * @details Outputs: none
Index: firmware/App/Modes/ModeStandby.h
===================================================================
diff -u -rd325999b7b3ea03b7e294cb8a0b97df93812fbe9 -r79b494c344417ba6865db01ad5f456e439bec1b2
--- firmware/App/Modes/ModeStandby.h	(.../ModeStandby.h)	(revision d325999b7b3ea03b7e294cb8a0b97df93812fbe9)
+++ firmware/App/Modes/ModeStandby.h	(.../ModeStandby.h)	(revision 79b494c344417ba6865db01ad5f456e439bec1b2)
@@ -34,31 +34,32 @@
 /// Standby mode data structure
 typedef struct
 {
-    U32 timeout;                        ///< Timeout.
-    U32 countdown;                      ///< Count down.
+    U32 timeout;                                        ///< Timeout.
+    U32 countdown;                                      ///< Count down.
 } STANDBY_MODE_DATA_T;
 
 // ********** public function prototypes **********
 
-void initStandbyMode( void );           // initialize this module
-U32 transitionToStandbyMode( void );    // prepares for transition to standby mode
-U32  execStandbyMode( void );           // execute the standby mode state machine (call from OperationModes)
+void initStandbyMode( void );                           // initialize this module
+U32 transitionToStandbyMode( void );                    // prepares for transition to standby mode
+U32  execStandbyMode( void );                           // execute the standby mode state machine (call from OperationModes)
 
-void waterSampleCommandHandler( SAMPLE_WATER_CMD_T sampleWaterCmd );
-BOOL requestDGStart( void );            // HD requests DG start (go to generation idle mode)
+void waterSampleCommandHandler( SAMPLE_WATER_CMD_T sampleWaterCmd );  // handle water sample command
+BOOL requestDGStart( void );                            // HD requests DG start (go to generation idle mode)
 
-BOOL startDGFlush( void );              // HD start flush mode
-BOOL startDGHeatDisinfect( void );      // HD start heat disinfect mode
+BOOL signalAbortWaterSampling( void );                  // HD signal to abort water sampling.
+BOOL startDGFlush( void );                              // HD start flush mode
+BOOL startDGHeatDisinfect( void );                      // HD start heat disinfect mode
 BOOL startDGHeatDisinfectActiveCool( void );
-DG_STANDBY_MODE_STATE_T getCurrentStandbyState( void );  // get the current state of the standby mode.
+DG_STANDBY_MODE_STATE_T getCurrentStandbyState( void ); // get the current state of the standby mode.
 
-BOOL testSetFilterFlushTimePeriodOverride( U32 value );
-BOOL testResetFilterFlushTimePeriodOverride( void );
+BOOL startDGChemicalDisinfect( void );                  // HD start chemical disinfect mode
+BOOL startDGChemicalDisinfectFlush( void );             // HD start chemical disinfect flush mode
 
-BOOL startDGChemicalDisinfect( void );       // HD start chemical disinfect mode
-BOOL startDGChemicalDisinfectFlush( void );  // HD start chemical disinfect flush mode
+BOOL startDGROPermeateSample( void );                   // HD start RO permeate sample
 
-BOOL startDGROPermeateSample( void );        // HD start RO permeate sample
+BOOL testSetFilterFlushTimePeriodOverride( U32 value ); // set filter flush time period override.
+BOOL testResetFilterFlushTimePeriodOverride( void );    // reset filter flush time period override.
 
 /**@}*/
 
Index: firmware/App/Services/SystemCommMessages.c
===================================================================
diff -u -rd325999b7b3ea03b7e294cb8a0b97df93812fbe9 -r79b494c344417ba6865db01ad5f456e439bec1b2
--- firmware/App/Services/SystemCommMessages.c	(.../SystemCommMessages.c)	(revision d325999b7b3ea03b7e294cb8a0b97df93812fbe9)
+++ firmware/App/Services/SystemCommMessages.c	(.../SystemCommMessages.c)	(revision 79b494c344417ba6865db01ad5f456e439bec1b2)
@@ -1101,6 +1101,10 @@
         {
             result = requestDGStop();
         }
+        else if ( ( DG_MODE_STAN == dgMode ) && ( FALSE == startingTreatment.start ) )
+        {
+            result = signalAbortWaterSampling();
+        }
     }
 
     sendAckResponseMsg( (MSG_ID_T)message->hdr.msgID, COMM_BUFFER_OUT_CAN_DG_2_HD, result );
@@ -1860,7 +1864,6 @@
 void sendROPermeateSampleDispenseReadyToHD( void )
 {
     MESSAGE_T msg;
-    U08 *payloadPtr = msg.payload;
 
     // Create a message record
     blankMessage( &msg );