Index: firmware/App/Controllers/DGInterface.h
===================================================================
diff -u -rb01542f8e4ef5a29e9b08fc0d465478de516bf02 -r30f049651877229042e3f8700c8596e5b9a1e0f4
--- firmware/App/Controllers/DGInterface.h	(.../DGInterface.h)	(revision b01542f8e4ef5a29e9b08fc0d465478de516bf02)
+++ firmware/App/Controllers/DGInterface.h	(.../DGInterface.h)	(revision 30f049651877229042e3f8700c8596e5b9a1e0f4)
@@ -52,8 +52,8 @@
 {
     DG_PRESSURE_SENSOR_RO_PUMP_INLET = 0,          ///< RO pump pressure sensor.
     DG_PRESSURE_SENSOR_RO_PUMP_OUTLET,             ///< RO pump pressure sensor.
-    DG_PRESSURE_SENSOR_DRAIN_PUMP_INLET,           ///< drain pump inlet pressure.
-    DG_PRESSURE_SENSOR_DRAIN_PUMP_OUTLET,          ///< drain pump outlet pressure.
+    DG_PRESSURE_SENSOR_DRAIN_PUMP_INLET,           ///< Drain pump inlet pressure.
+    DG_PRESSURE_SENSOR_DRAIN_PUMP_OUTLET,          ///< Drain pump outlet pressure.
     NUM_OF_DG_PRESSURE_SENSORS                     ///< Number of pressure sensors.
 } DG_PRESSURE_SENSORS_T;
 
@@ -106,15 +106,25 @@
     F32 HtrTrimInternal;
 } DG_TEMPERATURES_T;
 
+/// Payload record structure for a drain reservoir command message.
+typedef struct
+{
+    U32  drainToVolumeML;
+    BOOL tareLoadCells;
+} DRAIN_RESERVOIR_CMD_PAYLOAD_T;
+
 // ********** public function prototypes **********
 
 void initDGInterface( void );
-void initTreatmentReservoirMgmt( void );
-void execTreatmentReservoirMgmt( void );
+void initPreTreatmentReservoirMgmt( void );
+void execPreTreatmentReservoirMgmt( void );
+void initTreatmentReservoirMgmt( void );
+void execTreatmentReservoirMgmt( void );
 
 DG_OP_MODE_T getDGOpMode( void );
 U32 getDGSubMode( void );
 DG_RESERVOIR_ID_T getDGActiveReservoir( void );
+DG_RESERVOIR_ID_T getDGInactiveReservoir( void );
 F32 getDGPressure( DG_PRESSURE_SENSORS_T sensorID );
 U32 getDGROPumpPressureSetPt( void );
 F32 getDGROPumpFlowRateMlMin( void );