Index: firmware/App/Modes/ModeTxParams.c
===================================================================
diff -u -r52e1d4487a69a1ef0475321084527c0ba86c0892 -raa6d45143096dfab776ce2ed7c775cfe2dd6db18
--- firmware/App/Modes/ModeTxParams.c	(.../ModeTxParams.c)	(revision 52e1d4487a69a1ef0475321084527c0ba86c0892)
+++ firmware/App/Modes/ModeTxParams.c	(.../ModeTxParams.c)	(revision aa6d45143096dfab776ce2ed7c775cfe2dd6db18)
@@ -38,14 +38,15 @@
 
 // ********** private definitions **********
 
-#define MAX_DIALYSATE_VOLUME_ML                 ( 150 * ML_PER_LITER )  ///< Maximum dialysate volume (in mL)
-#define MAX_HEPARIN_VOLUME_ML                   10                      ///< Maximum heparin volume ( in mL )
-
+#define MAX_HEPARIN_VOLUME_ML                   10.0F                   ///< Maximum heparin volume ( in mL )
 #define NO_HEPARIN_PRE_STOP_TIME_SET            0                       ///< Zero value indicates no Heparin pre-stop time was set by user
-
 #define NO_HEPARIN_TYPE_SET                     0xFFFFFFFF              ///< UI will send this value for Heparin type if Heparin not used
+
 #define INSTIT_CHEM_DISINFECT_ENABLE_RANGE      1                       ///< Institutional record chemical disinfect enable/disable allowable range
 
+#define SYRINGE_PUMP_PRIME_VOLUME_ML            0.353F                  ///< Target syringe prime volume (in mL).              TODO- move these to syringe pump controller when implemented
+#define SYRINGE_PUMP_FILL_VOLUME_OFFSET_ML      0.8F                    ///< Advised fill volume offset due to HW variance.
+
 /// Record for range and default of treatment parameters.
 typedef struct
 {
@@ -588,19 +589,30 @@
 static BOOL checkTreatmentParamsDependencies( U32 *reasons )
 {
     BOOL result = TRUE;
+    U32  txDur  = stagedParams[ TREATMENT_PARAM_TREATMENT_DURATION ].uInt;
+    U32  hepST  = stagedParams[ TREATMENT_PARAM_HEPARIN_STOP_TIME ].uInt;
+    F32  hepDR  = stagedParams[ TREATMENT_PARAM_HEPARIN_DISPENSE_RATE ].sFlt;
+    F32  hepBV  = stagedParams[ TREATMENT_PARAM_HEPARIN_BOLUS_VOLUME ].sFlt;
+    F32  txVol  = hepBV + ( hepDR * ( hepST / (F32)SEC_PER_MIN ) ) + SYRINGE_PUMP_PRIME_VOLUME_ML + SYRINGE_PUMP_FILL_VOLUME_OFFSET_ML;
 
     // Verify Heparin stop time is only set if Heparin dispense rate is set
-    if ( ( stagedParams[ TREATMENT_PARAM_HEPARIN_STOP_TIME ].uInt > 0 ) && ( stagedParams[ TREATMENT_PARAM_HEPARIN_DISPENSE_RATE ].sFlt < NEARLY_ZERO ) )
+    if ( ( hepST > 0 ) && ( hepDR < NEARLY_ZERO ) )
     {
         reasons[ TREATMENT_PARAM_HEPARIN_STOP_TIME ] = REQUEST_REJECT_REASON_HEPARIN_STOP_TIME_WITH_NO_DISPENSE;
         result = FALSE;
     }
     // Verify Heparin stop time does not exceed Tx duration
-    else if ( stagedParams[ TREATMENT_PARAM_HEPARIN_STOP_TIME ].uInt > stagedParams[ TREATMENT_PARAM_TREATMENT_DURATION ].uInt )
+    else if ( hepST > txDur )
     {
         reasons[ TREATMENT_PARAM_HEPARIN_STOP_TIME ] = REQUEST_REJECT_REASON_HEPARIN_STOP_TIME_EXCEEDS_DURATION;
         result = FALSE;
     }
+    // Verify Heparin stop time does not exceed max 10 mL Heparin volume
+    else if ( txVol > MAX_HEPARIN_VOLUME_ML )
+    {
+        reasons[ TREATMENT_PARAM_HEPARIN_STOP_TIME ] = REQUEST_REJECT_REASON_HEPARIN_VOLUME_EXCEEDS_10_ML;
+        result = FALSE;
+    }
 
     return result;
 }