Index: firmware/App/Modes/ModeDrain.c
===================================================================
diff -u -ra1452dc7f16d37db53930c3d73992098709d7915 -r24dd186948c13ae8e1ff88c14cc4f478e739ee0b
--- firmware/App/Modes/ModeDrain.c	(.../ModeDrain.c)	(revision a1452dc7f16d37db53930c3d73992098709d7915)
+++ firmware/App/Modes/ModeDrain.c	(.../ModeDrain.c)	(revision 24dd186948c13ae8e1ff88c14cc4f478e739ee0b)
@@ -15,6 +15,7 @@
 *
 ***************************************************************************/
 
+#include "ConcentratePumps.h"
 #include "ConductivitySensors.h"
 #include "DrainPump.h"
 #include "Heaters.h"
@@ -46,15 +47,23 @@
 #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.
 
+/// Time period to wait for concentrate lines to rinse.
+#define RINSE_CONCENTRATE_LINES_WAIT    ( 25 * MS_PER_SECOND / TASK_GENERAL_INTERVAL )
+/// Reserver the concentrate speed to rinse out concentrate lines.
+#define RINSE_SPEED                     ( CONCENTRATE_PUMP_MAX_SPEED * -1 )
+
 // ********** private data **********
 
 static DG_DRAIN_STATE_T drainState;                                         ///< Currently active drain state.
 static U32 drainEmptyTareTimerCtr;                                          ///< Timer counter for delay between drain complete and load cell tare.
+static BOOL rinseConcentrateLines;                                          ///< Flag indicates to rinse concentrate lines.
+static U32 rinseConcentrateLinesTimerCtr;                                   ///< Timer counter for rinsing concentrate lines.
 
 // ********** private function prototypes **********
 
 static DG_DRAIN_STATE_T handleDrainState( void );
 static DG_DRAIN_STATE_T handleTareState( void );
+static DG_DRAIN_STATE_T handleRinseState( void );
 
 /*********************************************************************//**
  * @brief
@@ -67,6 +76,8 @@
 {
     drainState = DG_DRAIN_STATE_START;
     drainEmptyTareTimerCtr = 0;
+    rinseConcentrateLines = FALSE;
+    rinseConcentrateLinesTimerCtr = 0;
 }
 
 /*********************************************************************//**
@@ -135,6 +146,10 @@
             drainState = handleTareState();
             break;
 
+        case DG_DRAIN_STATE_RINSE:
+            drainState = handleRinseState();
+            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;
@@ -146,6 +161,31 @@
 
 /*********************************************************************//**
  * @brief
+ * The getCurrentDrainState function returns the current state of the drain mode.
+ * @details Inputs: drainState
+ * @details Outputs: none
+ * @return the current state of drain mode.
+ *************************************************************************/
+DG_DRAIN_STATE_T getCurrentDrainState( void )
+{
+    return drainState;
+}
+
+/*********************************************************************//**
+ * @brief
+ * The signalDrainModeRinseConcentrateLines function sets the flag for drain
+ * mode to rinse concentrate lines.
+ * @details Inputs: none
+ * @details Outputs: rinseConcentrateLines
+ * @return none
+ *************************************************************************/
+void signalDrainModeRinseConcentrateLines( BOOL rinse )
+{
+    rinseConcentrateLines = rinse;
+}
+
+/*********************************************************************//**
+ * @brief
  * The handleDrainState function handles the drain state of the drain mode
  * state machine.
  * @details Inputs: none
@@ -201,25 +241,52 @@
     {
         drainEmptyTareTimerCtr = 0;
         tareLoadCellsAtEmpty( inactiveReservoir );
-        requestNewOperationMode( DG_MODE_GENE );
 
         setValveState( VRD1, VALVE_STATE_CLOSED );
         setValveState( VRD2, VALVE_STATE_CLOSED );
+
+        if ( TRUE == rinseConcentrateLines )
+        {
+            setConcentratePumpTargetSpeed( CONCENTRATEPUMPS_CP1_ACID, RINSE_SPEED );
+            setConcentratePumpTargetSpeed( CONCENTRATEPUMPS_CP2_BICARB, RINSE_SPEED );
+            requestConcentratePumpOn( CONCENTRATEPUMPS_CP1_ACID );
+            requestConcentratePumpOn( CONCENTRATEPUMPS_CP2_BICARB );
+        }
+        rinseConcentrateLinesTimerCtr = 0;
+        result = DG_DRAIN_STATE_RINSE;
     }
 
     return result;
 }
 
 /*********************************************************************//**
  * @brief
- * The getCurrentDrainState function returns the current state of the drain mode.
- * @details Inputs: drainState
- * @details Outputs: none
- * @return the current state of drain mode.
+ * The handleRinseState function handles the tare state of the drain mode
+ * state machine.
+ * @details Inputs: drainEmptyTareTimerCtr
+ * @details Outputs: drainEmptyTareTimerCtr
+ * @return the next state
  *************************************************************************/
-DG_DRAIN_STATE_T getCurrentDrainState( void )
+static DG_DRAIN_STATE_T handleRinseState( void )
 {
-    return drainState;
+    DG_DRAIN_STATE_T result = DG_DRAIN_STATE_RINSE;
+
+    if ( TRUE == rinseConcentrateLines )
+    {
+        if ( ++rinseConcentrateLinesTimerCtr > RINSE_CONCENTRATE_LINES_WAIT )
+        {
+            rinseConcentrateLinesTimerCtr = 0;
+            requestConcentratePumpOff( CONCENTRATEPUMPS_CP1_ACID );
+            requestConcentratePumpOff( CONCENTRATEPUMPS_CP2_BICARB );
+            requestNewOperationMode( DG_MODE_GENE );
+        }
+    }
+    else
+    {
+        requestNewOperationMode( DG_MODE_GENE );
+    }
+
+    return result;
 }
 
 /**@}*/
Index: firmware/App/Modes/ModeDrain.h
===================================================================
diff -u -r54f45c387430e440ab4607451fc84dea61f273f1 -r24dd186948c13ae8e1ff88c14cc4f478e739ee0b
--- firmware/App/Modes/ModeDrain.h	(.../ModeDrain.h)	(revision 54f45c387430e440ab4607451fc84dea61f273f1)
+++ firmware/App/Modes/ModeDrain.h	(.../ModeDrain.h)	(revision 24dd186948c13ae8e1ff88c14cc4f478e739ee0b)
@@ -38,6 +38,7 @@
 U32 execDrainMode( void );          // execute the drain mode state machine
 
 DG_DRAIN_STATE_T getCurrentDrainState( void );  // get the current state of the drain mode.
+void signalDrainModeRinseConcentrateLines( BOOL rinse );    // Signal drain mode to rinse concentrate lines.
 
 /**@}*/
 
Index: firmware/App/Services/Reservoirs.c
===================================================================
diff -u -rcbcd41ec1ac2d5ae6446ec206ed6991a5306c249 -r24dd186948c13ae8e1ff88c14cc4f478e739ee0b
--- firmware/App/Services/Reservoirs.c	(.../Reservoirs.c)	(revision cbcd41ec1ac2d5ae6446ec206ed6991a5306c249)
+++ firmware/App/Services/Reservoirs.c	(.../Reservoirs.c)	(revision 24dd186948c13ae8e1ff88c14cc4f478e739ee0b)
@@ -18,6 +18,7 @@
 #include <string.h>     // for memcpy()
 
 #include "LoadCell.h"
+#include "ModeDrain.h"
 #include "ModeGenIdle.h"
 #include "OperationModes.h"
 #include "Reservoirs.h"
@@ -327,6 +328,7 @@
         {
             drainVolumeTargetMl.data = drainCmd.targetVolume;
             tareLoadCellRequest = drainCmd.tareLoadCell;
+            signalDrainModeRinseConcentrateLines( drainCmd.rinseConcentrateLines );
             requestNewOperationMode( DG_MODE_DRAI );
             cmdResponse.rejected = FALSE;
         }
Index: firmware/App/Services/Reservoirs.h
===================================================================
diff -u -re6f3a632890f96a5aa282922d11df148bdd06587 -r24dd186948c13ae8e1ff88c14cc4f478e739ee0b
--- firmware/App/Services/Reservoirs.h	(.../Reservoirs.h)	(revision e6f3a632890f96a5aa282922d11df148bdd06587)
+++ firmware/App/Services/Reservoirs.h	(.../Reservoirs.h)	(revision 24dd186948c13ae8e1ff88c14cc4f478e739ee0b)
@@ -46,8 +46,9 @@
 /// Drain command data structure.
 typedef struct
 {
-    U32 targetVolume;       ///< Target volume to drain to (in mL)
-    BOOL tareLoadCell;      ///< Flag to tare load call
+    U32 targetVolume;                   ///< Target volume to drain to (in mL)
+    BOOL tareLoadCell;                  ///< Flag to tare load cell or not
+    BOOL rinseConcentrateLines;         ///< Flag indicates to rinse concentrate lines or not
 } DRAIN_CMD_T;
 
 /// DG command response data record.