RPZ Backflow Devices Explained for Eastern Iowa Owners

If you have a sprinkler system, there's a good chance you also have a brass or bronze device near your foundation or along the supply line, with a couple of valves and a small port underneath. That's an RPZ, short for reduced pressure zone assembly. It's easy to ignore until someone tells you it needs a test. Here's what it does and why it matters.

What an RPZ does

An RPZ is a backflow preventer. Its job is to keep water from your irrigation system from flowing backward into the drinking water supply. Normally water only moves one way: from the main, into your pipes, out through the heads. The RPZ is a one-way gate with a safety valve built in, so that if something tries to reverse the flow, the water doesn't make it back into the clean side.

Why the reverse flow is a problem

Think about what a sprinkler head sits in. It's at ground level, surrounded by soil, lawn fertilizer, pet waste, and sometimes puddles after a storm. Water in those lines isn't water you'd want to drink.

Under normal conditions that doesn't matter, because the pressure from the supply keeps everything moving outward. But pressure can drop. A water main break, heavy water use somewhere nearby or work on the supply line can lower the pressure in the main, and a pressure drop can pull water backward through the pipes. Without protection, irrigation water could be drawn into the drinking supply. The RPZ is the protection.

Why it gets tested

An RPZ is a mechanical device. Inside are check valves and a relief valve held shut by springs and seals. Over time those parts wear, and a small piece of debris can keep a valve from seating. A device that looks fine from the outside can fail to do its job, and you can't tell by looking.

That's why backflow devices get tested. A certified tester connects gauges, checks that each valve holds the pressure it should, and records the result. If your municipality asks for test paperwork, it wants proof that the device is protecting the water supply. What your municipality requires, and how often, is its own rule, so ask your water utility or let your irrigation contractor tell you what they see locally.

How Fleming handles it

Fleming Irrigation has six employees certified by the state to test RPZ backflow devices. The service covers the whole job: the test, the paperwork, and submitting that paperwork to the municipality. You don't have to figure out which form goes where or who it goes to.

A customer named Todd Wirtner described his test in a Google review: “Scott J. Was the tech that preformed the test on my backflow system. He was very friendly and helpful.” A test is usually short, and a tech who explains what they're doing makes it easier on you.

The RPZ also comes into play at two other points in the year. In the fall, Fleming removes it as part of winterization and stores it in a heated space, so freezing doesn't damage it. In the spring, the start-up includes testing the RPZ if your municipality requires it.

What you can do to help

• Keep the area around the device clear of mulch, shrubs and stored items so a tester can get to it.
• Leave it alone. Don't paint it, wrap it or adjust the valves.
• If you see water running from the small port under the device, call. That relief port opens when something is wrong.
• Keep your test paperwork somewhere you can find it, in case the municipality asks.

If your installer never mentioned the device or the test when the system went in, it's fair to ask who handles it now. Plenty of owners don't know their system has one until a notice arrives.

A short checklist for the year

Test when your municipality asks. Have it removed and stored in the fall. Have it checked in the spring. Call if it drips. That's the whole routine, and it keeps both your lawn and your neighbors' tap water clean.

If you're not sure whether your RPZ is due for a test, call Fleming Irrigation at (319) 393-9229 or reach out through the contact page. We serve Cedar Rapids, Hiawatha, Marion, North Liberty, Iowa City, Coralville, Tiffin, Solon and Mount Vernon.