At the end of the shift, the missing volume of a sump is not only due to carry-off. It is also due to the evaporation of the water within the mixture during the machining process. Since water composes up to 95% of the volume, even a slight evaporation rate can change the overall concentration significantly. You will need to do a calculation by volume to determine the appropriate concentration for the refill. Please refer to the example below. To note, evaporation rates may be different between machines and/or processes. It is best to calculate this rate per machine sump and per process to ensure consistent concentrations. Example Known Factors:Desired Sump Concentration: 5%Total Sump Capacity: 50 gallonsVolume of Make-up Solution Needed: 25 gallonsCurrent Sump Concentration: 8%Unknown Factors:Required Make-up Concentration Calculation:Determine the volume of concentrate needed for the entire sump (volume of 50 gallons at the desired concentration of 5%):(.05 x 50 = 2.5 gallons of concentrate)Determine the volume of concentrate needed for a make-up solution if only 25 gallons are remaining in sump at 8% concentration:(25 x .08 = 2.0 gallons of concentrate) Then(2.5 gallons of concentrate originally in entire sump)-2.0 gallons in remaining sump.5 gallons of concentrate needed for make-upDetermine concentration for make-up solution:(.5 gal of conc. ÷ 25 gal fluid required = .02, or 2% conc.) Answer:The sump now needs to be filled with a 25 gallon make-up batch at a concentration of 2%.