Index: firmware/App/Modes/ModeDrain.c
===================================================================
diff -u -rebbb1f85550a1f9b8f946655f7b2b63f76fbf67d -rcea079b61dbd17b2ddaec99b1124248147d14e72
--- firmware/App/Modes/ModeDrain.c	(.../ModeDrain.c)	(revision ebbb1f85550a1f9b8f946655f7b2b63f76fbf67d)
+++ firmware/App/Modes/ModeDrain.c	(.../ModeDrain.c)	(revision cea079b61dbd17b2ddaec99b1124248147d14e72)
@@ -17,6 +17,7 @@
 
 #include "ConductivitySensors.h"
 #include "DrainPump.h"
+#include "Heaters.h"
 #include "ModeDrain.h"
 #include "OperationModes.h"
 #include "Pressures.h"
@@ -33,19 +34,26 @@
 
 // ********** 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 TARGET_DRAIN_PUMP_RPM           2100                                ///< Target drain pump speed (in RPM).
+#define DRAIN_WEIGHT_UNCHANGE_TIMEOUT   ( 2 * MS_PER_SECOND )               ///< Time period of unchanged weight during draining before timeout.
+/// Time period to wait after drain complete and before taring load cells.
+#define DRAIN_EMPTY_TARE_WAIT           ( MS_PER_SECOND / TASK_GENERAL_INTERVAL )
 
 #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.
 
+#define DELAY_RES_DRAIN_VALVE_MS        1000                                ///< Delay reservoir drain valve open by 1 second.
+#define DELAY_DRAIN_PUMP_MS             2000                                ///< Delay drain pump on by 2 seconds.
+
 // ********** 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
@@ -57,6 +65,7 @@
 void initDrainMode( void )
 {
     drainState = DG_DRAIN_STATE_START;
+    drainEmptyTareTimerCtr = 0;
 }
 
 /*********************************************************************//**
@@ -71,10 +80,27 @@
     // re-initialize each time we transition to drain mode
     initDrainMode();
 
+#ifndef V_2_SYSTEM
+    DG_RESERVOIR_ID_T inactiveReservoir = getInactiveReservoir();
+
+    if ( DG_RESERVOIR_1 == inactiveReservoir )
+    {
+        setValveStateDelayed( VRD1, VALVE_STATE_OPEN, DELAY_RES_DRAIN_VALVE_MS );
+    }
+    else if ( DG_RESERVOIR_2 == inactiveReservoir )
+    {
+        setValveStateDelayed( VRD2, VALVE_STATE_OPEN, DELAY_RES_DRAIN_VALVE_MS );
+    }
+#endif
     // set initial actuator states
     setValveState( VDR, VALVE_STATE_DRAIN_C_TO_NO );
-    setDrainPumpTargetRPM( TARGET_DRAIN_PUMP_RPM );
+    setDrainPumpTargetRPMDelayed( TARGET_DRAIN_PUMP_RPM, DELAY_DRAIN_PUMP_MS );
+
+    // NOTE: The target flow rate should be set prior to setting the start primary heater
+    // because the initial guess in the heaters driver needs the target flow to calculate
+    // the new PWMs for the main and small primary heaters
     setROPumpTargetFlowRate( TARGET_RO_FLOW_RATE_L, TARGET_RO_PRESSURE_PSI );
+    startPrimaryHeater();
 }
 
 /*********************************************************************//**
@@ -96,13 +122,20 @@
     switch ( drainState )
     {
         case DG_DRAIN_STATE_START:
-            drainState = DG_DRAIN_STATE_DRAIN;
+            if ( TRUE == isDrainPumpOn() )
+            {
+                drainState = DG_DRAIN_STATE_DRAIN;
+            }
             break;
 
         case DG_DRAIN_STATE_DRAIN:
             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;
@@ -114,9 +147,10 @@
 
 /*********************************************************************//**
  * @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 )
@@ -125,10 +159,57 @@
     DG_RESERVOIR_ID_T inactiveReservoir = getInactiveReservoir();
 
     // if we have reached our target drain to volume (by weight) or cannot drain anymore, we are done draining - go back to re-circ mode
-    if ( hasTargetDrainVolumeBeenReached( inactiveReservoir, DRAIN_WEIGHT_UNCHANGE_TIMEOUT ) )
+    if ( TRUE == hasTargetDrainVolumeBeenReached( inactiveReservoir, DRAIN_WEIGHT_UNCHANGE_TIMEOUT ) )
     {
         setDrainPumpTargetRPM( 0 );
+
+#ifndef V_2_SYSTEM
+        if ( DG_RESERVOIR_1 == inactiveReservoir )
+        {
+            setValveState( VRD1, VALVE_STATE_CLOSED );
+        }
+        else if ( DG_RESERVOIR_2 == inactiveReservoir )
+        {
+            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 );
+
+#ifndef V_2_SYSTEM
+        setValveState( VRD1, VALVE_STATE_CLOSED );
+        setValveState( VRD2, VALVE_STATE_CLOSED );
+#endif
     }
 
     return result;