Index: firmware/App/Modes/ModeDrain.c
===================================================================
diff -u -r1be40bede3bd1551577649959e3a38d171470f86 -r16d911f4c1a722fb179e8b88c784c2c05a073f6d
--- firmware/App/Modes/ModeDrain.c	(.../ModeDrain.c)	(revision 1be40bede3bd1551577649959e3a38d171470f86)
+++ firmware/App/Modes/ModeDrain.c	(.../ModeDrain.c)	(revision 16d911f4c1a722fb179e8b88c784c2c05a073f6d)
@@ -66,15 +66,8 @@
 #define ACID_PERCENT_FILL                        0.02222F                                              ///< Acid volume percentage of reservoir volume.
 #define DATA_PUBLISH_COUNTER_START_COUNT         70                                                    ///< Data publish counter start count.
 #define DRAIN_MODE_DATA_PUB_INTERVAL             ( MS_PER_SECOND / TASK_GENERAL_INTERVAL )             ///< Interval (ms/task time) at which the drain mode data is published on the CAN bus.
+#define MIN_CONCENTRATE_VOLUME_ML                500.0F                                                ///< Minimum concentrate volume in milliliters.
 
-///< Concentrate bottle acid low volume in mL.
-static const F32 CONCENTRATE_BOTTLE_ACID_LOW_VOLUME_ML   = ( CONCENTRATE_BOTTLE_PRIMING_VOL_ML +
-                                                             ( CONCENTRATE_BOTTLE_RESERVOIOR_VOL_ML * CONCENTRATE_BOTTLE_RESERVOIOR_FILLS * ACID_PERCENT_FILL) );
-
-///< Concentrate bottle bicarb low volume in mL.
-static const F32 CONCENTRATE_BOTTLE_BICARB_LOW_VOLUME_ML = ( CONCENTRATE_BOTTLE_PRIMING_VOL_ML +
-                                                             ( CONCENTRATE_BOTTLE_RESERVOIOR_VOL_ML * CONCENTRATE_BOTTLE_RESERVOIOR_FILLS * BICARB_PERCENT_FILL) );
-
 // ********** private data **********
 
 static DG_DRAIN_STATE_T drainState;                                                                    ///< Currently active drain state.
@@ -325,7 +318,7 @@
             getHDOperationMode( &hdMode );
 
             // Detect empty bottles using integrated volumes
-            if ( ( ( acidBottleVolML - getChemicalUsedVolumeML( ACID ) ) <= CONCENTRATE_BOTTLE_ACID_LOW_VOLUME_ML ) && // SRSDG 836
+            if ( ( ( acidBottleVolML - getChemicalUsedVolumeML( ACID ) ) <= MIN_CONCENTRATE_VOLUME_ML ) && // SRSDG 836
                  ( hdMode.hdMode != MODE_POST ) &&                            // don't care about concentrates after treatment complete
                  ( getTestConfigStatus( TEST_CONFIG_MIX_WITH_WATER ) != TRUE ) )
             {
@@ -340,7 +333,7 @@
                 }
             }
 
-            if ( ( ( bicarbBottleVolML - getChemicalUsedVolumeML( BICARB ) ) <= CONCENTRATE_BOTTLE_BICARB_LOW_VOLUME_ML ) &&  // SRSDG 837
+            if ( ( ( bicarbBottleVolML - getChemicalUsedVolumeML( BICARB ) ) <= MIN_CONCENTRATE_VOLUME_ML ) &&  // SRSDG 837
                  ( hdMode.hdMode != MODE_POST ) &&                            // don't care about concentrates after treatment complete
                  ( getTestConfigStatus( TEST_CONFIG_MIX_WITH_WATER ) != TRUE ) )
             {