Index: firmware/App/Modes/ModeDrain.c
===================================================================
diff -u -r66cc826068b54bc436cde0fae70a05ba6c1ac974 -r1722e975682c9e41e0b75551ada1139d3dc522a6
--- firmware/App/Modes/ModeDrain.c	(.../ModeDrain.c)	(revision 66cc826068b54bc436cde0fae70a05ba6c1ac974)
+++ firmware/App/Modes/ModeDrain.c	(.../ModeDrain.c)	(revision 1722e975682c9e41e0b75551ada1139d3dc522a6)
@@ -38,30 +38,34 @@
 
 // ********** private definitions **********
 
-#define TARGET_DRAIN_PUMP_RPM           2300                                                  ///< Target drain pump speed (in RPM).
-#define DRAIN_WEIGHT_UNCHANGE_TIMEOUT   ( 2 * MS_PER_SECOND )                                 ///< Time period of unchanged weight during draining before timeout.
+#define TARGET_DRAIN_PUMP_RPM                    2300                                                  ///< Target drain pump speed (in RPM).
+#define DRAIN_WEIGHT_UNCHANGE_TIMEOUT            ( 2 * MS_PER_SECOND )                                 ///< Time period of unchanged weight during draining before timeout.
 
-#define DRAIN_EMPTY_TARE_WAIT           ( MS_PER_SECOND / TASK_GENERAL_INTERVAL )             /// Time period to wait after drain complete and before taring load cells.
+#define DRAIN_EMPTY_TARE_WAIT                    ( MS_PER_SECOND / TASK_GENERAL_INTERVAL )             /// Time period to wait after drain complete and before taring load cells.
 
-#define TARGET_RO_PRESSURE_PSI          130                                                   ///< Target pressure for RO pump.
-#define TARGET_RO_FLOW_RATE_L           0.3F                                                  ///< Target flow rate for RO pump.
+#define TARGET_RO_PRESSURE_PSI                   130                                                   ///< Target pressure for RO pump.
+#define TARGET_RO_FLOW_RATE_L                    0.3F                                                  ///< Target flow rate for RO pump.
 
-#define DELAY_RES_DRAIN_VALVE_MS        1000                                                  ///< Delay reservoir drain valve open by 1 second.
-#define DELAY_DRAIN_PUMP_MS             2000                                                  ///< Delay drain pump on by 2 seconds.
+#define DELAY_RES_DRAIN_VALVE_MS                 1000                                                  ///< Delay reservoir drain valve open by 1 second.
+#define DELAY_DRAIN_PUMP_MS                      2000                                                  ///< Delay drain pump on by 2 seconds.
 
-#define DIALYSATE_DRAIN_TIME_OUT        ( 2 * SEC_PER_MIN * MS_PER_SECOND )                   ///< Dialysate drain time out.
+#define DIALYSATE_DRAIN_TIME_OUT                 ( 2 * SEC_PER_MIN * MS_PER_SECOND )                   ///< Dialysate drain time out.
 
-#define RINSE_CONCENTRATE_LINES_WAIT    ( 25 * MS_PER_SECOND / TASK_GENERAL_INTERVAL )        ///< Time period to wait for concentrate lines to rinse.
+#define RINSE_CONCENTRATE_LINES_WAIT             ( 25 * MS_PER_SECOND / TASK_GENERAL_INTERVAL )        ///< Time period to wait for concentrate lines to rinse.
 
-#define RINSE_SPEED                     ( ( CONCENTRATE_PUMP_MAX_SPEED - 3.0F ) * -1.0F )     ///< Reserver the concentrate speed to rinse out concentrate lines.
+#define RINSE_SPEED                              ( ( CONCENTRATE_PUMP_MAX_SPEED - 3.0F ) * -1.0F )     ///< Reserver the concentrate speed to rinse out concentrate lines.
 
+#define ACID_CONCENTRATION_BOTTLE_VOLUME_ML      3430.0F                                               ///< Bottle volume of acid concentration in mL.
+#define BICARB_CONCENTRATION_BOTTLE_VOLUME_ML    3780.0F                                               ///< Bottle volume of bicarb concentration in mL.
+#define CONCENTRATION_BOTTLE_LOW_VOLUME_ML       100.0F                                                ///< Concentration bottle low volume in mL.
+
 // ********** private data **********
 
-static DG_DRAIN_STATE_T drainState;                                                           ///< Currently active drain state.
-static U32 drainEmptyTareTimerCtr;                                                            ///< Timer counter for delay between drain complete and load cell tare.
-static BOOL rinseConcentrateLines;                                                            ///< Flag indicates to rinse concentrate lines.
-static U32 rinseConcentrateLinesTimerCtr;                                                     ///< Timer counter for rinsing concentrate lines.
-static U32 dialysateDrainStartTime;                                                           ///< Dialysate drain start time.
+static DG_DRAIN_STATE_T drainState;                                                                    ///< Currently active drain state.
+static U32 drainEmptyTareTimerCtr;                                                                     ///< Timer counter for delay between drain complete and load cell tare.
+static BOOL rinseConcentrateLines;                                                                     ///< Flag indicates to rinse concentrate lines.
+static U32 rinseConcentrateLinesTimerCtr;                                                              ///< Timer counter for rinsing concentrate lines.
+static U32 dialysateDrainStartTime;                                                                    ///< Dialysate drain start time.
 
 // ********** private function prototypes **********
 static DG_DRAIN_STATE_T handleDrainStateStart( void );
@@ -243,15 +247,17 @@
             setValveState( VRD2, VALVE_STATE_CLOSED );
         }
 
-        // check for empty bottles at the end of drain
-        if ( TRUE == isEmptyAcidBottle() )                                // is acid volume < 10%
+        // Detect empty bottles using integrated volumes
+        if ( ( ( ACID_CONCENTRATION_BOTTLE_VOLUME_ML - getChemicalUsedVolumeML( ACID ) ) <= CONCENTRATION_BOTTLE_LOW_VOLUME_ML ) ) // ||  // SRSDG 437
         {
+            resetChemicalUsedVolumeML( ACID );
             setThisFisrtFillFlag( TRUE );                                 // indicates bottles need prime
-            activateAlarmNoData( ALARM_ID_DG_ACID_BOTTLE_LOW_VOLUME );    // trigger empty acid bottle alarm
+            activateAlarmNoData( ALARM_ID_DG_ACID_BOTTLE_LOW_VOLUME );
         }
 
-        if ( TRUE == isEmptyBicarbBottle() )
+        if ( ( ( BICARB_CONCENTRATION_BOTTLE_VOLUME_ML - getChemicalUsedVolumeML( BICARB ) ) <= CONCENTRATION_BOTTLE_LOW_VOLUME_ML ) )  // || // SRSDG 438
         {
+            resetChemicalUsedVolumeML( BICARB );
             setThisFisrtFillFlag( TRUE );
             activateAlarmNoData( ALARM_ID_DG_BICARB_BOTTLE_LOW_VOLUME );
         }