Index: firmware/App/Modes/ModePreTreat.c
===================================================================
diff -u -r231665843bcb057cab17d967fa1543d94a66c9df -re408267b7e73d664051a46e65ac248749af8e5be
--- firmware/App/Modes/ModePreTreat.c	(.../ModePreTreat.c)	(revision 231665843bcb057cab17d967fa1543d94a66c9df)
+++ firmware/App/Modes/ModePreTreat.c	(.../ModePreTreat.c)	(revision e408267b7e73d664051a46e65ac248749af8e5be)
@@ -992,6 +992,7 @@
         cmdStartDG();
     }
 
+    // Ensure any pending reservoir switches are completed before sending drain command
     if ( TRUE == hasDGCompletedReservoirSwitch() )
     {
         if ( ( DG_MODE_GENE == dgOpMode ) && ( DG_GEN_IDLE_MODE_STATE_FLUSH_WATER == dgSubMode ) )
@@ -1018,6 +1019,7 @@
     DG_CMD_RESPONSE_T dgCmdResp;
     DG_OP_MODE_T dgOpMode = getDGOpMode();
 
+    // Check DG response to drain command
     if ( TRUE == getDGCommandResponse( DG_CMD_START_DRAIN, &dgCmdResp ) )
     {
         if ( DG_CMD_REQUEST_REJECT_REASON_NONE == dgCmdResp.rejectCode )
@@ -1052,18 +1054,14 @@
 
     if ( ( DG_MODE_GENE == dgOpMode ) && ( DG_GEN_IDLE_MODE_STATE_FLUSH_WATER == dgSubMode ) )
     {
-        // if fills not yet enabled, check to see if we want to move on to drain the other reservoir
-        if ( reservoirFlags[ DG_RESERVOIR_1 ].startFlushFill != TRUE )
+        // Drain both reservoirs and return to active res 2 before initial fills
+        if ( ( initialReservoirDrain[ inactiveReservoir ] != TRUE ) || ( inactiveReservoir != DG_RESERVOIR_1 ) )
         {
-            if ( ( initialReservoirDrain[ inactiveReservoir ] != TRUE ) ||
-                 ( inactiveReservoir != DG_RESERVOIR_1 ) )
-            {
-                initialReservoirDrain[ inactiveReservoir ] = TRUE;
-                state = PRE_TREATMENT_RESERVOIR_MGMT_REQUEST_RESERVOIR_SWITCH_STATE;
-            }
+            initialReservoirDrain[ inactiveReservoir ] = TRUE;
+            state = PRE_TREATMENT_RESERVOIR_MGMT_REQUEST_RESERVOIR_SWITCH_STATE;
         }
-
-        else
+        // Once both reservoirs drained and returned to active res 2, wait for pre-tx workflow to get to point where fills allowed before filling
+        else if ( TRUE == reservoirFlags[ DG_RESERVOIR_1 ].startFlushFill )
         {
             volume = getPreTreatmentFillVolume( inactiveReservoir );
 
@@ -1243,7 +1241,6 @@
     {
         if ( DG_CMD_REQUEST_REJECT_REASON_INVALID_MODE == dgCmdResp.rejectCode )
         {
-
             state = PRE_TREATMENT_RESERVOIR_MGMT_REQUEST_RESERVOIR_SWITCH_STATE;
         }
         else if ( dgCmdResp.rejectCode != DG_CMD_REQUEST_REJECT_REASON_NONE )