Backflow testing that keeps you compliant and your water safe

Water in your plumbing is supposed to flow one way, from the public main into your building. Under certain conditions, such as a sudden pressure drop from a water main break or firefighting, or pressure in your system exceeding the supply pressure, water can reverse direction. That reversal, called backflow, can pull water from irrigation systems, boilers, fire sprinkler lines or commercial equipment back into the drinking water supply.

A backflow prevention assembly is a mechanical device with check valves and, in some designs, a relief valve that stops reverse flow. Because these devices rely on springs, seals and moving parts, they can wear out or become fouled. Regular testing confirms that each check valve holds and each relief valve opens at the correct pressure.

Water providers and local codes commonly require testing when an assembly is installed, after repairs and at regular intervals, often annually. Testing must be done by a certified backflow tester using calibrated test equipment, and results are reported to the water provider.

Different hazards call for different assemblies. A reduced pressure zone assembly, often called an RPZ, has two independent check valves with a relief valve between them. If either check fails or pressure conditions reverse, the relief valve opens and discharges water to prevent backflow. RPZs are used where the potential contaminant could be a health hazard, such as boiler chemicals or certain commercial processes. Because they discharge water when they detect a problem, they must be installed where that water can drain safely.

A double check valve assembly uses two check valves without a relief valve and is used for lower hazard applications, including many fire sprinkler systems. A pressure vacuum breaker, common on residential irrigation, protects against back-siphonage and must be installed above the highest sprinkler head. Each type has a specific test procedure, and the tester must follow it exactly. The requirement for which type is needed on your property comes from your water provider and local plumbing code.

A backflow test is usually straightforward, but a little preparation helps it go smoothly. The tester needs access to the assembly and its test cocks, so clear away vegetation, stored items or snow around outdoor assemblies. Assemblies in vaults may require the lid to be opened and any standing water removed before testing.

During the test, water to the assembly may be shut off briefly. For businesses, it helps to schedule testing at a time when a short interruption will not affect operations. For irrigation systems, testing is often done when the system is being activated for the season.

It is helpful to have any previous test reports and the notice from your water provider available. These documents list the assembly's make, model, size and serial number and identify the reporting requirements. If the assembly has been replaced or repaired since the last test, note the changes.

After testing, the results are documented on the form required by your provider. If the assembly passes, the report is submitted or provided to you for submission. If it fails, repairs are quoted and scheduled, and a retest is performed after the work to complete compliance.