Backflow Prevention & RPZ Testing

What is backflow, and why does anyone care?

Drinking water systems work because pressure always pushes clean water toward you. Backflow is that flow running in reverse — a water main break or a big hydrant draw suddenly drops street pressure, and water gets siphoned backward from private plumbing into the public supply. If what siphons back is boiler water, irrigation runoff, or anything from a commercial process, one building's problem becomes the neighborhood's drinking water problem. Backflow preventers exist to make that reversal physically impossible at the property line.

What an RPZ actually does

The device most commercial properties are required to have is a reduced pressure zone assembly — an RPZ. It is two spring-loaded check valves in series with a monitored pressure chamber between them, and a relief valve underneath that dumps water on the floor rather than ever letting contaminated water push backward. That is worth knowing because an RPZ that occasionally spits from its relief port is often doing its job, not failing — and one that dumps constantly is telling you a check has fouled. Either way, it fails safe: outward, visibly, never backward.

Why the annual test is mandatory, not a suggestion

An RPZ is a mechanical device with springs and rubber that wear, and you cannot tell whether it still holds by looking at it. That is why water utilities require an annual test by a certified tester, with results filed to the city — and why the letters escalate to water shut-off warnings when ignored. The requirement typically covers commercial buildings, irrigation systems, fire sprinkler connections, boilers with chemical treatment, and similar cross-connections. The deadline is real: utilities do disconnect service over lapsed backflow compliance.

What happens during a test visit

A certified tester connects a calibrated gauge kit to the assembly's test cocks, briefly isolates the device, and measures whether each check valve and the relief valve hold their required pressures. It takes roughly half an hour per device, water is off only for minutes, and the paperwork gets filed with your utility. If the device fails, the usual fix is a rebuild kit — new checks and rubber in the existing body — rather than a whole new assembly. Failed devices are common after winter, especially on irrigation systems that were not properly winterized.

Getting testing handled without the runaround

The practical answer for a business is a shop that tests, repairs, and files the paperwork in one visit — and remembers your deadline next year. Hanna handles backflow prevention and RPZ testing across Marion, Cedar Rapids, and the Corridor as part of our commercial plumbing work, licensed and insured (Iowa Contractors #C145148, Plumbing & Mechanical #50273-CL), with hourly commission-free techs. If your device tests clean, you pay for a test, not a rebuild you didn't need.