Watts 20mm Stainless RPZD Reduced Pressure Zone Device With Ball Valves, Unions & Strainer 009-SS-020-ULBS backflow preventers provide protection of the potable water supply in accordance with national plumbing codes and water authority requirements. Series SS009 can be used in a variety of health hazard installations whenever the downstream liquid is of a composition which may damage bronze material or it is desirable to eliminate trace elements of lead and copper. Typical applications are: Industrial or plant use, medical/diagnostic equipment, reverse osmosis systems, carbonated beverage machines, breweries/distillers, paper and pulp industry, chemical plants and aggressive atmospheres. The SS009-AUS series features two in-line independent check valves, captured springs, replaceable check seats, corrosion resistant internal parts and a hydraulically operated differential pressure relief valve. All sizes are constructed with NPT body connections and are standardly furnished with vandal resistant test cocks. Series SS009-AUS QT models are furnished with 316 stainless steel, full port, investment cast, quarter turn ball valve shutoffs.