Index: firmware/App/Controllers/SpentChamberFill.c
===================================================================
diff -u -re6415d33321e7990c3b5e82b0c8a87c64cc3a2c8 -r56410a2475a4a6d1aa93642c630cdf37683d3231
--- firmware/App/Controllers/SpentChamberFill.c	(.../SpentChamberFill.c)	(revision e6415d33321e7990c3b5e82b0c8a87c64cc3a2c8)
+++ firmware/App/Controllers/SpentChamberFill.c	(.../SpentChamberFill.c)	(revision 56410a2475a4a6d1aa93642c630cdf37683d3231)
@@ -1,17 +1,17 @@
 /**************************************************************************
 *
-* Copyright (c) 2024-2025 Diality Inc. - All Rights Reserved.
+* Copyright (c) 2025-2026 Diality Inc. - All Rights Reserved.
 *
 * THIS CODE MAY NOT BE COPIED OR REPRODUCED IN ANY FORM, IN PART OR IN
 * WHOLE, WITHOUT THE EXPLICIT PERMISSION OF THE COPYRIGHT OWNER.
 *
 * @file    SpentChamberFill.c
 *
-* @author  (last)      Vinayakam Mani
-* @date    (last)      20-Aug-2025
+* @author  (last)      Sameer Kalliadan Poyil
+* @date    (last)      03-Feb-2026
 *
 * @author  (original)  Vinayakam Mani
-* @date    (original)  20-Aug-2025
+* @date    (original)  21-Aug-2025
 *
 ***************************************************************************/
 
@@ -39,6 +39,7 @@
 // ********** private definitions **********
 
 #define SPENT_CHAMBER_FILL_DATA_PUBLISH_INTERVAL           ( 250 / TASK_GENERAL_INTERVAL )      ///< Interval (ms/task time) at which the balancing chamber data published.
+#define SPENT_CHAMBER_SWITCHING_PERIOD                     59                                   ///< Spent Chamber Fill Switching Period to max dialysate flow rate Qd: 600 minus 50ms to stabilize the valve closure
 
 // ********** private data **********
 
@@ -53,6 +54,7 @@
 
 // ********** private function prototypes **********
 
+static SPENT_CHAMBER_FILL_EXEC_STATE_T handleSpentChamberFillWaitPressureStabilizeState( void );
 static SPENT_CHAMBER_FILL_EXEC_STATE_T handleSpentChamberFillState1FillStart( void );
 static SPENT_CHAMBER_FILL_EXEC_STATE_T handleSpentChamberState1DosingControl( void );
 static SPENT_CHAMBER_FILL_EXEC_STATE_T handleSpentChamberFillState1FillEnd(void);
@@ -95,8 +97,8 @@
 {
     initSpentChamberFill();
     updateBalChamberSwitchingPeriod();
-    // Follow the same cycle for spent chamber fill
-    spentChamberFillSwitchingPeriod = getBalChamberSwitchingPeriod();
+    // Update the Switching Period to max dialysate flow rate(Qd: 600) for filling spent chamber at max rate.
+    spentChamberFillSwitchingPeriod = SPENT_CHAMBER_SWITCHING_PERIOD;
 }
 
 /*********************************************************************//**
@@ -118,9 +120,13 @@
     switch ( spentChamberFillExecState )
     {
         case SPENT_CHAMBER_FILL_STATE_START:
-            spentChamberFillExecState = SPENT_CHAMBER_FILL_STATE1_FILL_START;
+            spentChamberFillExecState = SPENT_CHAMBER_FILL_WAIT_PRESSURE_STABILIZE_STATE;
             break;
 
+        case SPENT_CHAMBER_FILL_WAIT_PRESSURE_STABILIZE_STATE:
+            spentChamberFillExecState = handleSpentChamberFillWaitPressureStabilizeState();
+            break;
+
         case SPENT_CHAMBER_FILL_STATE1_FILL_START:
             spentChamberFillExecState = handleSpentChamberFillState1FillStart();
             break;
@@ -182,6 +188,32 @@
 
 /*********************************************************************//**
  * @brief
+ * The handleSpentChamberFillWaitPressureStabilizeState  function introduces the pressure
+ * stabilization period before starting the spent chamber fill.
+ * @details \b Inputs: none
+ * @details \b Outputs: valve states
+ * @return none.
+ *************************************************************************/
+static SPENT_CHAMBER_FILL_EXEC_STATE_T handleSpentChamberFillWaitPressureStabilizeState(  void )
+{
+    SPENT_CHAMBER_FILL_EXEC_STATE_T nextState = SPENT_CHAMBER_FILL_WAIT_PRESSURE_STABILIZE_STATE;
+
+    F32 freshDialPressure = getFilteredPressure( D18_PRES );
+    F32 spentDialPressure = getFilteredPressure( D51_PRES );
+
+    BOOL spentInRange = ( ( spentDialPressure >= SPENT_DIAL_FILL_PRESSURE_MIN_PSIG ) && ( spentDialPressure <= SPENT_DIAL_FILL_PRESSURE_MAX_PSIG ) );
+    BOOL freshInRange = ( ( freshDialPressure >= FRESH_DIAL_FILL_PRESSURE_MIN_PSIG ) && ( freshDialPressure <= FRESH_DIAL_FILL_PRESSURE_MAX_PSIG ) );
+
+    if ( ( TRUE == spentInRange  )  && ( TRUE == freshInRange )  )
+    {
+        nextState = SPENT_CHAMBER_FILL_STATE1_FILL_START;
+    }
+
+    return nextState;
+}
+
+/*********************************************************************//**
+ * @brief
  * The valveControlForSCFillState2FillStart function actuates the valve combination
  * for state 2 fill process.
  * @details \b Inputs: none
@@ -228,8 +260,8 @@
         //Valve control for state 1 spent chamber fill
         valveControlForSCFillState1FillStart();
         // start acid and bicarb pump with the expected quantity
-        setConcentratePumpTargetSpeed( D11_PUMP, CONCENTRATE_PUMP_MAX_SPEED, acidDoseVolume );
-        setConcentratePumpTargetSpeed( D10_PUMP, CONCENTRATE_PUMP_MAX_SPEED, bicarbDoseVolume );
+        setConcentratePumpTargetSpeed( D11_PUMP, DOSING_CONCENTRATE_PUMP_SPEED, acidDoseVolume );
+        setConcentratePumpTargetSpeed( D10_PUMP, DOSING_CONCENTRATE_PUMP_SPEED, bicarbDoseVolume );
         requestConcentratePumpOn( D11_PUMP );
         requestConcentratePumpOn( D10_PUMP );
 
@@ -317,8 +349,8 @@
         // Valve control for state 2 fill
         valveControlForSCFillState2FillStart();
         // start acid and bicarb pump with the expected quantity
-        setConcentratePumpTargetSpeed( D11_PUMP, CONCENTRATE_PUMP_MAX_SPEED, acidDoseVolume );
-        setConcentratePumpTargetSpeed( D10_PUMP, CONCENTRATE_PUMP_MAX_SPEED, bicarbDoseVolume );
+        setConcentratePumpTargetSpeed( D11_PUMP, DOSING_CONCENTRATE_PUMP_SPEED, acidDoseVolume );
+        setConcentratePumpTargetSpeed( D10_PUMP, DOSING_CONCENTRATE_PUMP_SPEED, bicarbDoseVolume );
         requestConcentratePumpOn( D11_PUMP );
         requestConcentratePumpOn( D10_PUMP );