Backflow Preventers

60 backflow prevention devices from Watts, Zurn Wilkins, Apollo-Conbraco, Arrowhead Brass, Caleffi North America, Cash Acme, Aalberts Integrated Piping and Moen. Assemblies run 1/4" through 3"; air gap fittings cover 1/2" through 6". Most of the range is lead free bronze or lead free brass.

The device class is set by the hazard, not by the pipe size. A reduced pressure principle assembly — the RP, or RPZ where it is built as a reduced pressure zone assembly — is what a high hazard connection needs: it has a relief port that dumps to atmosphere the moment either check fouls, so a failure is visible on the floor instead of silent in the potable line. A double check assembly is a low hazard device and fails closed without telling anyone. A pressure vacuum breaker (PVB) protects against back-siphonage only, not back-pressure, which is why it belongs on irrigation and not on a boiler fill. Substituting down a class because it fits the budget is the one substitution that is never a field call.

On a lawn irrigation or sprinkler system the local code decides between a PVB and an RPZ backflow preventer, and the answer usually turns on whether fertilizer or chemical is injected downstream. A hose bib backflow preventer — a hose connection vacuum breaker threaded onto the sillcock — is the cheapest protection in the building and the one most often missing; eight are stocked here, four of them Watts in 3/4". A residential service entrance is typically a dual check, stocked from 1/4" through 1".

27 of the 60 are testable assemblies. Every reduced pressure, reduced pressure zone and double check assembly here carries test cocks, and in most jurisdictions has to be certified by a licensed tester at installation and then annually. That annual obligation follows the building, so specifying a testable assembly where the code does not require one commits the owner to a recurring cost.

Where the manufacturer publishes limits, the devices are rated 175 psi maximum working pressure and 180°F maximum temperature. ASSE 1013 covers reduced pressure principle assemblies and ASSE 1015 covers double checks; the number on the tag is what the inspector reads.

Rebuilding beats replacing on these. Eight Zurn Wilkins backflow preventer repair kits cover the 375, 375XL, 950XL, 975XL and 975XL2 from 1/4" through 2" — rubber and spring kits for an annual test failure, complete internals when the seats are cut. Match the kit to the model number on the tag, not to the pipe size.

The range breaks down as: reduced pressure principle (RP) assemblies (14), hose connection vacuum breakers (8), repair kits and internals (8), reduced pressure zone (RPZ) assemblies (7), double check valve assemblies (6), dual check valves (6), atmospheric and anti-siphon vacuum breakers (5), air gap fittings (4), pressure vacuum breaker (1), and a 2" Cash Acme EB45-U.

Backflow devices sit alongside check valves, pressure reducing valves and mixing valves in our valve reference guide.