ProMinent 7746928 20-200 SCFH CO2 Feeder - The ProMinent CO2 Feeder is designed to utilize Carbon Dioxide (CO2) in the control of pH levels in pools and spas. There are several advantages when using CO2 for pH control compared to acid. Adding CO2 will not contribute to a TDS increase in water, thus reducing the amount of make-up water required to maintain the water quality. It is much safer, as there is no mineral acid solution or fumes present on-site, which solves the problems associated with handling acid and corrosive fumes.