TUSA RS790 RegulatorTUSA s RS 790 Regulator The all chrome plated marine brass first stage regulator is a balanced diaphragm design which is environmentally sealed The diaphragm membrane transmits the pressure changes to the internal mechanism eliminating the need for the surrounding water to enter the intricate mechanism The benefit of this type of first stage design is that none of the internal parts are exposed to contaminants such as salt sand chlorine or pool acids