What Is a Backflow Preventer and Why Does Your Sprinkler System Need One?

If you've ever had a sprinkler system installed or gotten a bid for one, you've probably heard the term backflow preventer come up — and seen it as a line item on the estimate. Most homeowners nod along without fully understanding what it is, what it does, or why it's required. It's one of those components that operates completely in the background, never demands your attention, and is easy to forget about — right up until something goes wrong or you realize it needs attention before winter.

Here's a straightforward explanation of what a backflow preventer actually does, why it's legally required on every irrigation system in Nebraska, and what you need to know as a homeowner to keep yours in good shape.

What is backflow and why does it matter?

To understand what a backflow preventer does, it helps to understand the problem it's solving. Your home's water supply operates under positive pressure — water flows from the municipal supply into your home and out through your fixtures in one direction. That positive pressure is what keeps the system clean and safe.

Backflow happens when that pressure is disrupted and water flows in reverse — back toward the municipal supply rather than away from it. In an irrigation system, this is a real concern. Your sprinkler heads are sitting in soil that contains fertilizers, pesticides, lawn chemicals, and naturally occurring bacteria and contaminants. If a pressure drop in the municipal supply causes water to reverse direction, those contaminants can be drawn back into the pipe and potentially into your home's drinking water supply.

This isn't a theoretical risk — it's a well-documented problem that water utilities take seriously enough to require protection on every irrigation system. That protection is the backflow preventer.

How a backflow preventer works

A backflow preventer is a mechanical device installed at the point where your irrigation system connects to your home's water supply. It uses a series of check valves — one-way valves that allow water to flow in only one direction — to physically prevent water from reversing back into the supply line under any conditions.

There are several types of backflow preventers used in residential irrigation. The two most common in the Omaha area are the pressure vacuum breaker, commonly called a PVB, and the reduced pressure zone device, commonly called an RP. Both accomplish the same goal of preventing backflow but through slightly different mechanisms and with different levels of protection. The type required for your system depends on factors including the elevation of your irrigation heads relative to the device and local code requirements.

Your irrigation contractor will specify the appropriate type during the design and bidding process. If you're not sure which type your system has, it's typically the device located above ground near your water meter or where the irrigation line exits the house — a cylindrical or rectangular assembly with a valve handle and sometimes a test port.

Why a licensed plumber has to install it in Nebraska

Here's something that surprises many homeowners when they get their first irrigation bid — in Nebraska, the backflow preventer must be installed by a licensed plumber, not the irrigation contractor. This is a state requirement designed to ensure that the connection to your potable water supply is made by someone licensed and accountable for that type of work.

What this means practically is that your irrigation bid and your plumbing work are two separate scopes. Your irrigation contractor — like Alternate Rain — handles the design and installation of the system itself, while a licensed plumber handles the backflow preventer connection to your water supply. Both pieces of work need to happen for the system to be complete and code-compliant.

This is something every reputable irrigation company should be transparent about upfront. The plumbing portion of the job represents a meaningful part of the overall cost of a new sprinkler installation, and homeowners deserve to understand why that cost exists before they commit to a project. If an irrigation company quotes you a system without mentioning the backflow preventer or the licensed plumber requirement, that's worth asking about before you sign anything.

What you need to do with it every fall

Here's where the backflow preventer becomes relevant to your annual maintenance routine. Because it's located above ground and contains water, it's vulnerable to freezing during Nebraska winters. If water is left inside the device when temperatures drop below freezing, that water expands, the device cracks, and you're looking at a replacement — and potentially water damage — come spring.

The good news is that winterizing your backflow preventer is straightforward. Depending on the type of device you have, winterization typically involves closing the shutoff valve to the irrigation system, opening a small drain valve or cap on the device to release the water inside, and in some cases removing the device entirely and storing it indoors until spring.

Our Sprinkler System Info page has detailed instructions for winterizing both PVB and RP style backflow preventers. If you've never done it before, we're happy to walk you through it during your spring startup visit so you know exactly what to do when fall arrives.

If you're enrolled in our Seasonal Care Package, backflow preventer winterization is covered as part of your fall visit — one less thing to remember before the first freeze.

What happens if the backflow preventer fails?

Like any mechanical device, backflow preventers can wear out over time. Seals degrade, internal springs lose tension, and the check valves can fail to seat properly. A failing backflow preventer may leak at the device itself, allow pressure to drop in your irrigation system, or in the worst case fail to prevent backflow as intended.

Signs that your backflow preventer may need attention include water dripping or leaking from the device between watering cycles, a noticeable drop in pressure across your system, or the device failing a required test. Many municipalities require periodic backflow preventer testing by a certified tester to confirm the device is functioning properly. If you're not sure whether your device has been tested or when it was last inspected, it's worth having it looked at during your next service visit.

If you have questions about your backflow preventer or want to schedule a service visit, give us a call at (402) 289-4019 or contact us online. It's a small component that does a very important job — and making sure it's in good shape is one of the easiest ways to protect both your irrigation system and your home's water supply.