Index: firmware/App/Modes/FPModes/ModePreGenPermeate.c
===================================================================
diff -u -rf7553872983e440277cae7f84b386ff195d7c394 -r886964fa2bf6a5bb61b33b8b5547f3d0c585b360
--- firmware/App/Modes/FPModes/ModePreGenPermeate.c	(.../ModePreGenPermeate.c)	(revision f7553872983e440277cae7f84b386ff195d7c394)
+++ firmware/App/Modes/FPModes/ModePreGenPermeate.c	(.../ModePreGenPermeate.c)	(revision 886964fa2bf6a5bb61b33b8b5547f3d0c585b360)
@@ -448,67 +448,6 @@
 
 /*********************************************************************//**
  * @brief
- * The validatePreGenPChangeReq function validate whether requested
- * sub mode change is legal or not.
- * @details \b Inputs: none
- * @details \b Outputs: none
- * @return TRUE if request is legal, FALSE if not.
- *************************************************************************/
-BOOL validatePreGenPChangeReq( U32 newSubMode )
-{
-    BOOL result = FALSE;
-    LEVEL_STATE_T level = getLevelStatus( P25_LEVL );
-
-    // TODO add validation logic
-    result = TRUE;
-
-    return result;
-}
-
-/*********************************************************************//**
- * @brief
- * The signalNewPreGenPSubMode function requests transition to a new
- * PreGen Permeate sub mode.
- * @details \b Inputs: none
- * @details \b Outputs: none
- * @return none
- *************************************************************************/
-void signalNewPreGenPSubMode( U32 newSubMode )
-{
-    FP_PRE_GENP_MODE_STATE_T reqSubMode = (FP_PRE_GENP_MODE_STATE_T)newSubMode;
-
-    if ( reqSubMode < NUM_OF_FP_PRE_GENW_MODE_STATES )
-    {
-        preGenPState = reqSubMode;
-        // handle the prerequisite if any
-        switch ( reqSubMode )
-        {
-            case FP_PRE_GENP_INLET_PRESSURE_CHECK:
-                break;
-
-            case FP_PRE_GENP_FILTER_FLUSH:
-                break;
-
-            case FP_PRE_GENP_PERMEATE_FLUSH:
-                break;
-
-            case FP_PRE_GENP_CONCENTRATE_FLUSH:
-                // jump to concentrate flush sub mode only if the permeate tank is full
-                break;
-
-            case FP_PRE_GENP_VERIFY_WATER:
-                break;
-
-            case FP_PRE_GENP_PAUSED:
-            default:
-                break;
-        }
-        setModePreGenPTransition( reqSubMode );
-    }
-}
-
-/*********************************************************************//**
- * @brief
  * The getPreGenWDataPublishInterval function gets the pre generate water
  * mode data publish interval.
  * @details \b Inputs: genWaterDataPublishInterval
@@ -612,4 +551,71 @@
     return result;
 }
 
+/*********************************************************************//**
+ * @brief
+ * The testValidatePreGenPChangeReq function validate whether requested
+ * sub mode change is legal or not.
+ * @details \b Inputs: none
+ * @details \b Outputs: none
+ * @param newSubMode the enumerated sub state of the mode.
+ * @return TRUE if request is legal, FALSE if not.
+ *************************************************************************/
+BOOL testValidatePreGenPChangeReq( U32 newSubMode )
+{
+    BOOL result = FALSE;
+    LEVEL_STATE_T level = getLevelStatus( P25_LEVL );
+
+    if ( newSubMode < NUM_OF_FP_PRE_GENW_MODE_STATES )
+    {
+        switch ( newSubMode )
+        {
+            case FP_PRE_GENP_CONCENTRATE_FLUSH:
+                result = (( LEVEL_STATE_HIGH == level ) ? TRUE : FALSE);
+                break;
+
+            case FP_PRE_GENP_INLET_PRESSURE_CHECK:
+            case FP_PRE_GENP_FILTER_FLUSH:
+            case FP_PRE_GENP_PERMEATE_FLUSH:
+            case FP_PRE_GENP_VERIFY_WATER:
+            case FP_PRE_GENP_PAUSED:
+            default:
+                result = TRUE;
+                break;
+        }
+    }
+
+    return result;
+}
+
+/*********************************************************************//**
+ * @brief
+ * The testSignalNewPreGenPSubMode function requests transition to a new
+ * PreGen Permeate sub mode.
+ * @details \b Inputs: none
+ * @details \b Outputs: none
+ * @param newSubMode the enumerated sub state of the mode.
+ * @return none
+ *************************************************************************/
+void testSignalNewPreGenPSubMode( U32 newSubMode )
+{
+    if ( newSubMode < NUM_OF_FP_PRE_GENW_MODE_STATES )
+    {
+        preGenPState = (FP_PRE_GENP_MODE_STATE_T)newSubMode;
+        // handle the prerequisite if any
+        switch ( newSubMode )
+        {
+            // Require no special handling for now (update the comment if required in future)
+            case FP_PRE_GENP_INLET_PRESSURE_CHECK:
+            case FP_PRE_GENP_FILTER_FLUSH:
+            case FP_PRE_GENP_PERMEATE_FLUSH:
+            case FP_PRE_GENP_CONCENTRATE_FLUSH:
+            case FP_PRE_GENP_VERIFY_WATER:
+            case FP_PRE_GENP_PAUSED:
+            default:
+                break;
+        }
+        setModePreGenPTransition( preGenPState );
+    }
+}
+
 /**@}*/