used on gas, oil or electric, direct-fired, residential water heater and hot water storage tank applications to absorb the increased volume of water created by thermal expansion. It also maintains balanced pressure throughout the water supply system by keeping system pressure below the T&P relief valve setting. It is a pre-pressurized, field-adjustable steel tank with an FDA approved Butyl rubber diaphragm and brass 3/4 in (20 mm) inlet connection. An expansion membrane prevents air-to-water contact in the tank ensuring a long system life. IAMPO listed and ANSI/NSF 61 certified. Maximum pressure 150psi (10 bar).