Index: firmware/App/Modes/Prime.c
===================================================================
diff -u -r19fc8f015489be63932eed969d28329d123332e0 -r70ccc0b282f1dafcd1f6b95dd53f4efe2efd3b2b
--- firmware/App/Modes/Prime.c	(.../Prime.c)	(revision 19fc8f015489be63932eed969d28329d123332e0)
+++ firmware/App/Modes/Prime.c	(.../Prime.c)	(revision 70ccc0b282f1dafcd1f6b95dd53f4efe2efd3b2b)
@@ -46,9 +46,12 @@
 
 #define PRIME_DRAIN_RESERVOIR_TO_VOLUME_ML      0                                                   ///< Drain reservoir to this volume (in mL) during prime.
 
-// TODO: Determine the appropriate fill volume for each reservoir during prime state
-#define PRIME_FILL_RESERVOIR_TO_VOLUME_ML       ( FILL_RESERVOIR_TO_VOLUME_ML / 2 )                 ///< Fill reservoir to this volume (in mL) during prime.
+#define PRIME_CONSUMED_DIALYSATE_VOLUME_ML      100                                                 ///< Volume of dialysate consumed during prime.
 
+/// Fill reservoir 1 to this volume (in mL) during prime.
+#define PRIME_FILL_RESERVOIR_ONE_VOLUME_ML      ( FILL_RESERVOIR_TO_VOLUME_ML - PRIME_CONSUMED_DIALYSATE_VOLUME_ML )
+#define PRIME_FILL_RESERVOIR_TWO_VOLUME_ML      500                                                 ///< Fill reservoir 2 to this volume (in mL) during prime.
+
 #define NO_AIR_DETECTED_COUNT                   ( 10 * MS_PER_SECOND )                              ///< No air detected time period count.
 #define PURGE_AIR_TIME_OUT_COUNT                ( 30 * MS_PER_SECOND )                              ///< Time period count for purge air time out.
 #define MIN_LOAD_CELL_STEADY_VOLUME_TIME        ( 10 * MS_PER_SECOND )                              ///< Minimum time load cell reading need to remain steady in ms.
@@ -305,10 +308,10 @@
         signalDialInPumpHardStop();
         signalBloodPumpHardStop();
 
-        primeStopRequested = FALSE;
-        primePauseStartTime   = getMSTimerCount();
-        previousPrimeState    = currentPrimeState;
-        currentPrimeState     = HD_PRIME_PAUSE;
+        primeStopRequested  = FALSE;
+        primePauseStartTime = getMSTimerCount();
+        previousPrimeState  = currentPrimeState;
+        currentPrimeState   = HD_PRIME_PAUSE;
     }
 }
 
@@ -357,7 +360,6 @@
     DG_OP_MODE_T dgOpMode = getDGOpMode();
     U32 dgSubMode = getDGSubMode();
 
-
     // treatment reservoir mgmt. state machine
     switch ( currentReservoirMgmtState )
     {
@@ -405,7 +407,15 @@
             if ( ( DG_MODE_CIRC == dgOpMode ) && ( DG_RECIRCULATE_MODE_STATE_RECIRC_WATER == dgSubMode ) )
             {
                 currentReservoirMgmtState = PRIME_RESERVOIR_MGMT_WAIT_FOR_FILL_CMD_RESP;
-                cmdStartDGFill( PRIME_FILL_RESERVOIR_TO_VOLUME_ML );
+
+                if ( DG_RESERVOIR_1 == getDGInactiveReservoir() )
+                {
+                    cmdStartDGFill( PRIME_FILL_RESERVOIR_ONE_VOLUME_ML );
+                }
+                else
+                {
+                    cmdStartDGFill( PRIME_FILL_RESERVOIR_TWO_VOLUME_ML );
+                }
             }
             break;