Like we mentioned before, depending on the different factors involved in your specific cleaning process, chemical and water will be consumed at different rates. For starters, water has a boiling point of 100°C but we might not heat the solution that high. Usually, it is up to 60°C, but it is enough to increase the evaporation rate of the water present in the solution. We lose most of the water from the process through that. The chemical has a much higher boiling point so less components of the chemical are being lost. Usually, we lose more chemical through drag gout than we do through evaporation or the exhaust. Therefore, we would have to replace more quantity of water than chemical. This is why we initially set the controller to half the desired concentration than we want to keep in the process. Once it is fine tuned to your specific process factors, the set point might be higher or lower than that reference, but it is a good baseline to start.