Index: firmware/App/Modes/Dialysis.c
===================================================================
diff -u -r825a299f4ad0f4a51b203c3f5d730c6978ab6844 -r7334590e610cd1543e128ad2dbc0de17e824b619
--- firmware/App/Modes/Dialysis.c	(.../Dialysis.c)	(revision 825a299f4ad0f4a51b203c3f5d730c6978ab6844)
+++ firmware/App/Modes/Dialysis.c	(.../Dialysis.c)	(revision 7334590e610cd1543e128ad2dbc0de17e824b619)
@@ -62,6 +62,8 @@
 static F32 measUFVolume;                                ///< Current total measured volume for ultrafiltration (Where are we w/r/t ultrafiltration).
 static F32 resStartVolume[ NUM_OF_DG_RESERVOIRS ];      ///< Reservoir start volume for ultrafiltration (i.e. where did we start with each reservoir).
 static F32 resFinalVolume[ NUM_OF_DG_RESERVOIRS ];      ///< Reservoir final volume for ultrafiltration (i.e. where did we end after switch with each reservoir).
+static F32 resCurrVolume[ NUM_OF_DG_RESERVOIRS ];       ///< Reservoir current volume.
+static F32 resLastVolume[ NUM_OF_DG_RESERVOIRS ];       ///< Reservoir previous volume.
 static F32 measUFVolumeFromPriorReservoirs;             ///< Current total ultrafiltration volume from previous reservoirs in current treatment.
 
 static U32 uFTimeMS;                                    ///< Current elapsed ultrafiltration time (in ms).  Used for calculating UF reference volume.
@@ -1065,7 +1067,7 @@
     LOAD_CELL_ID_T loadCell = ( activeRes == DG_RESERVOIR_1 ? LOAD_CELL_RESERVOIR_1_PRIMARY : LOAD_CELL_RESERVOIR_2_PRIMARY );
     F32 latestResVolume = getLoadCellWeight( loadCell );
 #ifndef DISABLE_UF_ALARMS
-    F32 deltaVolume = latestResVolume - resFinalVolume[ activeRes ];
+    F32 deltaVolume = latestResVolume - resLastVolume[ activeRes ];
 
     // ensure volume change is not too excessive - indication that load cell was impacted by some kind of shock
     if ( fabs(deltaVolume) > MAX_ACTIVE_LOAD_CELL_CHANGE_G )
@@ -1139,4 +1141,22 @@
     measUFVolumeFromPriorReservoirs += ( resFinalVolume[ inactiveRes ] - resStartVolume[ inactiveRes ] );
 }
 
+/*********************************************************************//**
+ * @brief
+ * The updateReservoirVolumes function updates the reservoir volumes based
+ * on new load cell readings.
+ * @details Inputs: none
+ * @details Outputs: resCurrVolume[], resLastVolume[]
+ * @param res1Vol new volume for reservoir 1
+ * @param res2Vol new volume for reservoir 2
+ * @return none
+ *************************************************************************/
+void updateReservoirVolumes( F32 res1Vol, F32 res2Vol )
+{
+    resLastVolume[ DG_RESERVOIR_1 ] = resCurrVolume[ DG_RESERVOIR_1 ];
+    resLastVolume[ DG_RESERVOIR_2 ] = resCurrVolume[ DG_RESERVOIR_2 ];
+    resCurrVolume[ DG_RESERVOIR_1 ] = res1Vol;
+    resCurrVolume[ DG_RESERVOIR_2 ] = res2Vol;
+}
+
 /**@}*/