The first stage is a balanced diaphragm design. 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. These environmental contaminants cause corrosion and mineral deposits to form on the internal mechanism deteriorating regulator performance. The standard diaphragm regulator does allow water into the mainspring chamber so that the diaphragm can perform this transmission of pressure changes. The first stage has 4 low pressure (LP) and 2 high pressure (HP) ports and is made from durable corrosion resistant chrome plated brass.