Product details:

Thermal expansion occurs as domestic water is heated. Left unchecked, the resulting pressure increase can cause relief valve discharge and other potentially unsafe conditions. Therm-X-Trol expansion tanks absorb this expanded water, keeping water pressure at a safe level. Water heater manufacturers and plumbing codes require the installation of an expansion control device if a backflow preventor, pressure reducing valve or check valve is installed in the domestic supply line. Therm-X-Trol satisfies all manufacturers' requirements.