- Shut off the main water supply so the overall water pressure in the building being tested is neutral.
- Locate the backflow valve and, using the diagrams on the valve, determine the direction water flows through the valve.
- Bleed test cocks to free them of dirt and accumulated water pressure by turning them open using a screwdriver.
- Insert the differential gauge's low pressure hose into the test cock closest to the water supply (the upstream cock).
- Insert the differential gauge's high pressure hose into the downstream test cock.
- Bleed the high-pressure hose and the low-pressure hose to clear any air or water from the gauge. Record the pressure differential between the two segments. A differential pressure of at least 1 psid indicates a working and tightly sealed pressure gauge.
- Turn the building's main water supply back on.
How do I Test a Backflow Valve?
Backflow valves, also known as check valves, allow water to flow only in one direction. When installed properly, backflow valves prevent water from entering a homeowner's water system and becoming contaminated then re-entering the public water supply. Check valves may also be installed in different segments of a home's water system to segregate laundry or sprinkler systems from drinking water. Most municipalities require that backflow valves be installed and maintained and sometimes require a qualified technician's certification that they operate properly.