Index: firmware/App/Modes/ModeDrain.c
===================================================================
diff -u -r2e3b3b2034ee5afb52a8630568145c9705afff9f -r78a138b18328bce8312abac79d76aad9dfe8ea3a
--- firmware/App/Modes/ModeDrain.c	(.../ModeDrain.c)	(revision 2e3b3b2034ee5afb52a8630568145c9705afff9f)
+++ firmware/App/Modes/ModeDrain.c	(.../ModeDrain.c)	(revision 78a138b18328bce8312abac79d76aad9dfe8ea3a)
@@ -34,7 +34,8 @@
 // ********** private definitions **********
 
 #define TARGET_DRAIN_PUMP_RPM           1800                                ///< Target drain pump speed (in RPM).
-#define DRAIN_WEIGHT_UNCHANGE_TIMEOUT    ( 2 * MS_PER_SECOND )              ///< Time period of unchanged weight during draining before timeout.
+#define DRAIN_WEIGHT_UNCHANGE_TIMEOUT   ( 2 * MS_PER_SECOND )               ///< Time period of unchanged weight during draining before timeout.
+#define DRAIN_EMPTY_TARE_WAIT           ( MS_PER_SECOND )                   ///< Time period to wait after drain complete and before taring load cells.
 
 #define TARGET_RO_PRESSURE_PSI          130                                 ///< Target pressure for RO pump.
 #define TARGET_RO_FLOW_RATE_L           0.3                                 ///< Target flow rate for RO pump.
@@ -44,11 +45,13 @@
 
 // ********** private data **********
 
-static DG_DRAIN_STATE_T drainState = DG_DRAIN_STATE_START;                  ///< Currently active drain state.
+static DG_DRAIN_STATE_T drainState;                                         ///< Currently active drain state.
+static U32 drainEmptyTareTimerCtr;                                          ///< Timer counter for delay between drain complete and load cell tare.
 
 // ********** private function prototypes **********
 
 static DG_DRAIN_STATE_T handleDrainState( void );
+static DG_DRAIN_STATE_T handleTareState( void );
 
 /*********************************************************************//**
  * @brief
@@ -60,6 +63,7 @@
 void initDrainMode( void )
 {
     drainState = DG_DRAIN_STATE_START;
+    drainEmptyTareTimerCtr = 0;
 }
 
 /*********************************************************************//**
@@ -121,6 +125,10 @@
             drainState = handleDrainState();
             break;
 
+        case DG_DRAIN_STATE_TARE:
+            drainState = handleTareState();
+            break;
+
         default:
             SET_ALARM_WITH_2_U32_DATA( ALARM_ID_DG_SOFTWARE_FAULT, SW_FAULT_ID_DRAIN_MODE_INVALID_EXEC_STATE, drainState )
             drainState = DG_DRAIN_STATE_START;
@@ -132,9 +140,10 @@
 
 /*********************************************************************//**
  * @brief
- * The handleDrainState function handles the drain state  of the drain mode state machine.
+ * The handleDrainState function handles the drain state of the drain mode
+ * state machine.
  * @details Inputs: none
- * @details Outputs: Drain out from reservoir
+ * @details Outputs: none
  * @return the next state
  *************************************************************************/
 static DG_DRAIN_STATE_T handleDrainState( void )
@@ -146,7 +155,6 @@
     if ( hasTargetDrainVolumeBeenReached( inactiveReservoir, DRAIN_WEIGHT_UNCHANGE_TIMEOUT ) )
     {
         setDrainPumpTargetRPM( 0 );
-        requestNewOperationMode( DG_MODE_CIRC );
 
 #ifndef V_2_SYSTEM
         if ( DG_RESERVOIR_1 == inactiveReservoir )
@@ -158,13 +166,45 @@
             setValveState( VRD2, VALVE_STATE_CLOSED );
         }
 #endif
+
+        if ( TRUE == isReservoirTarePending() )
+        {   // Tare reservoir load cells at empty if requested
+            result = DG_DRAIN_STATE_TARE;
+        }
+        else
+        {
+            requestNewOperationMode( DG_MODE_CIRC );
+        }
     }
 
     return result;
 }
 
 /*********************************************************************//**
  * @brief
+ * The handleTareState function handles the tare state of the drain mode
+ * state machine.
+ * @details Inputs: drainEmptyTareTimerCtr
+ * @details Outputs: drainEmptyTareTimerCtr
+ * @return the next state
+ *************************************************************************/
+static DG_DRAIN_STATE_T handleTareState( void )
+{
+    DG_DRAIN_STATE_T result = DG_DRAIN_STATE_TARE;
+    DG_RESERVOIR_ID_T inactiveReservoir = getInactiveReservoir();
+
+    if ( ++drainEmptyTareTimerCtr > DRAIN_EMPTY_TARE_WAIT )
+    {
+        drainEmptyTareTimerCtr = 0;
+        tareLoadCellsAtEmpty( inactiveReservoir );
+        requestNewOperationMode( DG_MODE_CIRC );
+    }
+
+    return result;
+}
+
+/*********************************************************************//**
+ * @brief
  * The getCurrentDrainState function returns the current state of the drain mode.
  * @details Inputs: drainState
  * @details Outputs: none