Irrigation backflow testing: which device your sprinkler system needs, when it is tested, and how to winterize it

The short answer: Colorado State University (CSU) Extension says backflow prevention devices "must be installed on all sprinkler systems" that use drinking water, and where that device is a testable assembly (a pressure vacuum breaker or a reduced pressure assembly), a certified tester checks it on a schedule your water utility sets. Irrigation is where the backflow rules meet the calendar: you drain the system in fall and refill it in spring, sometimes with a new pump or injector. Each step touches the rules: which device you need, when the test is due, whether draining counts as a reason to retest, and whether a replacement needs a permit.

This guide takes them in order, naming the rule behind each answer. Salt Lake City names "lawn sprinkling systems" first among residential cross-connections. The field test itself is covered in how backflow testing works. Prices and utility fees are in the backflow testing cost guide.

Why a lawn sprinkler system counts as a hazard

A sprinkler head spends most of its life retracted into the soil of a lawn that gets fertilizer, weed killer and dog traffic. A brochure from the University of Southern California Foundation for Cross-Connection Control and Hydraulic Research (USC FCCCHR), whose field test procedures Oregon's rule names (or approved equivalents) and Washington's rule cites, says it in one line: "Water pooling around sprinkler heads may be contaminated by chemicals, fertilizers, or animal waste."

The trouble starts when pressure on the supply side drops. CSU Extension describes the chain: "Any drop in pressure in the main city water line can result in back-siphonage backflow of fertilizers, pesticides, manures and other contaminants through sprinkler heads and the irrigation piping system into the potable water supply." The causes it lists are ordinary ones, a break in the line or heavy withdrawal "as may occur during firefighting operations" (CSU Extension, Home Sprinkler Systems: Backflow Prevention Devices, reviewed August 2025).

The second path is backpressure. CSU warns that an improperly installed lawn sprinkler pump or injector "may force contaminants back into the potable water supply," because the pump pushes harder than the city main. That is why the device choice below depends on whether anything on your side can push.

The garden hose belongs in the same picture. CSU says a hose connection vacuum breaker "should be used as minimum protection when fertilizers, insecticides or other pesticides are applied with a hose-end sprayer." The U.S. EPA's Cross-Connection Control Manual includes both the "lawn sprinkler system" and the "weedicide and fertilizer sprayer" aspirator in its partial list of plumbing hazards.

How often are household connections left unprotected? The best survey we found is old and small. USC FCCCHR inspected 188 single-family homes in one Iowa water system between May 2002 and January 2003 under an EPA grant. Unprotected hose bibs turned up in 91% of homes, and 95.7% had a direct or indirect cross-connection to a health hazard. Only five of the homes had an irrigation system, and one of the five was unprotected. The authors added that irrigation systems, "which are common in some parts of the country, could easily contribute to the potential for backflow occurrences in residences" (USC FCCCHR, Prevalence of Cross-Connections in Household Plumbing; report dated February 3, 2004).

Which backflow device an irrigation system needs

Four kinds of device show up on sprinkler lines. The atmospheric vacuum breaker (AVB) and the pressure vacuum breaker (PVB) protect only against backsiphonage. California's handbook says a PVB "is not to be used to protect from backpressure." The reduced pressure principle assembly (RP) protects against both backsiphonage and backpressure, and Salt Lake City rates it for health and non-health hazards. The double check (DC) also handles both directions, but California says it "may only be used to isolate low hazard cross-connections." Two questions decide which one your system gets. Can anything on your side push water backward: a pump, an injector, a second water source? And is anything added to the water that makes it a health hazard?

Sources: 30 TAC 344.50-344.51; WAC 246-290-490 Table 13; OAC 3745-95-05(D); California handbook 3.3.2 and Appendix D; Salt Lake City; Hastings; CSU Extension. Your utility can be stricter than its state.

Why an injector or a pump changes the answer

A PVB is one check valve plus an air inlet that opens when supply pressure falls. It can break a siphon. It cannot hold back water that is being pushed toward the main, which is exactly what a pump or a pressurized injector can do. Adding fertilizer also raises the stakes, because the water sitting in the pipes now carries the chemical. Both problems point to the same device. Texas requires an RP or an air gap once chemicals are involved, Hastings requires an RP, CSU's guidance names the RP, and Ohio withdraws its PVB option. Washington's air gap or RP list names premises with separate irrigation systems and chemical addition, such as parks and golf courses.

This is the change that catches homeowners: a PVB that passed for years no longer meets the Texas, Ohio or Hastings rules once an injector goes in. Texas puts the timing in the rule: the RP or air gap has to be in place "before any chemical is added." If you plan to add fertigation, a booster pump or a connection to a well or pond, ask your utility or permit office which device it wants before the work starts.

Height: why some yards get an RP without any chemicals

A PVB works by letting air into the line, so it has to sit above everything it protects. Texas, California and Hastings all require at least 12 inches above the highest downstream piping or sprinkler head, and Texas measures pop-up heads "from the retracted position from the top of the sprinkler" (30 TAC 344.50(b)(3)). On a sloped lot, the highest head may be above any spot where a PVB could go. CSU notes that RPs "are often used when pressure vacuum breakers cannot be used (i.e. when downstream piping is higher than the 12-inch clearance mentioned above)."

The AVB: a sprinkler device that usually is not tested

Some systems have an atmospheric vacuum breaker on each zone valve instead of one PVB at the supply. CSU describes it as gravity-operated and needed on each zone, and Salt Lake City's sheet says it must be installed 6 inches above the highest sprinkler head. Salt Lake City lists the AVB as "Not required to be tested annually." Washington has AVBs on irrigation systems inspected at installation, after a backflow incident and after repair, reinstallation or relocation, rather than tested yearly (WAC 246-290-490(7)(c)). If your notice names a testable assembly and you can only find AVBs on the zone valves, call the number on the notice before booking a tester.

How often the sprinkler device is tested

"Annual" is the common answer, but it is not universal, and irrigation is where the exceptions are. Texas' landscape irrigation rule requires a test "upon installation, repair, replacement, or relocation," and adds the annual test only for "irrigation systems designated as health hazards" (30 TAC 344.50(e)). Texas defines a health hazard as a situation involving any substance that "can cause death, illness, spread of disease" if it enters the drinking water supply (30 TAC 344.1). That leaves Texas cities room to set longer cycles for plain lawn systems, and some do.

Sources: each rule or utility's own page, listed below. The O'Fallon and Spokane pages are Internet Archive copies (May 13 and October 14, 2026).

The Minnesota date matters for older homes there: RPs "have had testing requirements for many years," but the duty for PVBs and other non-RP testable devices applies to installations made on or after January 23, 2016.

You still test a system you never turn on

Two utilities say plainly that the test does not lapse with the lawn. Spokane: "Even unused systems require annual testing because water sitting in the system can become contaminated." Gahanna's reason is that the system "is still physically connected to the public water supply." Both name the same way out: have the line to the irrigation system cut and capped. Gahanna inspects the cut and cap at no charge and then marks the system inactive. Spokane asks for photos of the capped line. If you reconnect later, Gahanna says you must tell the city, and annual testing starts again.

Spring start-up and the backflow test: which comes first

A spring start-up and a backflow test are two different jobs, and utilities treat them that way. Gahanna's FAQ explains the difference: "A spring startup service is performed on the irrigation system as whole to check for leaks, clogs, etc. A backflow test is specifically performed on the device itself to ensure that is working properly." The start-up date moves with the weather. The test date, Gahanna says, does not: "Testing the device once every 12 months after the previous test date is a firm deadline."

Example (Gahanna row of the table above): your device was last tested in May, and a warm spring means you want water in March. Gahanna's own advice is to have the start-up done in March and the backflow test in May, so your testing month stays the same every year.

Spokane instead suggests testing "ideally before you turn on your irrigation system." Either way, the tester has to be certified, and many utilities take results only from testers on their own list. Marin Water says that if a test is done by someone not on its list, it "cannot accept the test results." Gahanna notes the start-up technician may not be certified, so a second employee may test.

Example (California row): a sprinkler assembly in California is drained in November and refilled in April. The state handbook says a water system must ensure that all assemblies "installed for its Cross-Connection Control Program" are field tested "following installation, repair, depressurization for winterizing, or permanent relocation" (section 3.3.3(a)). The duty sits with the water system, so ask yours whether your sprinkler assembly is in its program and wants a test after a winter drain-down. If so, plan the test after the April refill.

A start-up order that works with all of these rules:

1. Find the due date on your notice or last report. Texas' test form puts annual tests "no more than 12 months from the last test date," not by calendar year.
2. Before turning the water back on, close the test cocks and ball valves you opened for winter. CSU says to open the ball valves slowly once the supply is on, because doing so "will prevent damage to the system that can be caused by water hammer."
3. Look at the device and the pipes on either side. University of Georgia Extension notes that with home irrigation "you probably wouldn't know you had any pipe damage until you turned it on for the first spring watering."
4. If the assembly cracked or leaks, it needs repair, and a repair triggers a test in Texas, Washington, California and Houston, among others.
5. Book a tester from your utility's list for a date inside your window. Find your utility in the backflow tester directory.
6. Keep a copy of the report. Gahanna says the tester submits a copy to the city, but keeping records "is your responsibility."

Winterizing a sprinkler backflow preventer

Sprinkler backflow devices sit at or above ground level, outside the soil that shelters buried pipe. CSU explains why freezing does so much damage: water contracts as it cools only until it reaches 39°F, then expands as it turns to ice, increasing "in volume by one-eleventh, so 11 cubic feet of water will form approximately 12 cubic feet of ice" (CSU Extension, Preparing Your Sprinkler System for Winter, reviewed August 2025). Salt Lake City's guide adds that "most sprinkling system piping is not below frost levels," and that water freezing in the backflow preventer or its ball valves "can cause internal damage or possible crack the device or valve." Even in Georgia, where only the top few inches of ground tend to freeze in most of the state, UGA Extension warns that "backflow prevention valves, are at ground level and could be in danger."

Two rule questions follow from winterizing, and both are for your utility. First, whether California's winterizing trigger covers your assembly, as above. Second, if you take the assembly off for winter: Washington's rule lists "reinstallation" among the events after which the purveyor must ensure an inspection or test, but does not say whether a spring re-mount counts. Ask before you plan on removing it. Freeze damage is simpler: a cracked body or a split valve is a repair or a replacement, and both bring a new test.

Replacing, moving or removing the device

Replacing a backflow preventer usually means a permit. CSU says permits "normally are required" for sprinkler systems that need backflow devices, with the device type and location approved in plan review. Minnesota's plumbing code requires a permit before installation, installation by a licensed plumber, and notice to the public water supplier within 30 days (Minnesota DLI fact sheet). The backflow test report form included in Hastings' irrigation permit packet states that "a plumbing permit is required for the installation, removal or replacement of all backflow preventers."

A new or moved device gets a new test. Texas requires one on installation, repair, replacement or relocation; Washington on installation, repair, reinstallation or relocation; Houston on installation, repair and relocation. California adds that a water system must receive a passing test "before providing continuous service to a water user with a newly installed BPA" (section 3.3.3(d)). Deadlines are short: ten business days for a Texas irrigator to send results, 10 days after installation in Salt Lake City, and 30 days in Minnesota.

Moving a device can also end its grandfather status. Oregon lets older assemblies that are no longer on the approved list stay in service only if "the assemblies are not moved, the piping systems are not significantly remodeled or modified," they are maintained, and they match the hazard (OAR 333-061-0070(14)). Salt Lake City lets an existing double check stay on a lawn system if it was installed under the previous code and tested annually, but will not accept a new one. Horseshoe Bay lets older non-RP devices on commercial, multi-family and HOA systems "remain until they fail and must be replaced," and new installations on those systems must be an RP above ground. Spokane answers the grandfathering question for homes directly: "All properties must comply with current backflow prevention requirements, regardless of how long you've lived there."

The replacement itself has to be an approved model. Oregon's rule (USC FCCCHR approval or an equivalent laboratory the state approves) and Spokane's guidance both point to the USC FCCCHR list. The Foundation says assemblies on its list are "approved for a period of three years and this approval is subject to renewal," that the list names the shutoff valves that may be used as replacements, and that "the use of shutoff valves other than those listed invalidates the Foundation's approval" (USC FCCCHR, List of Approved Backflow Prevention Assemblies). Costs for repair, replacement and permits are in the cost guide.

If you remove a device for good, tell the utility so its records match the yard. Houston asks your plumber, engineer or testing company to send a Backflow Prevention Assembly Removal Form.

Wells, ponds and secondary water on the same system

A second water source changes the device. Texas requires an RP or air gap whenever "any additional water source" connects to an irrigation system that is also on the potable supply (30 TAC 344.51(c)). Salt Lake City specifies an RP where secondary water is available, and CSU says Colorado's dual systems, which carry irrigation and potable water through the same pipes, need an RP. A system fed only by ditch water and never connected to the potable supply needs no backflow device, according to CSU.

The reason is the same backpressure problem. One of the illustrated cases in EPA's manual is a house whose city-supplied plumbing is connected by a valve to a private well used for lawn sprinkling, and the well is polluted by sewage seeping from a cesspool. During low city pressure, "possibly when lawn sprinkling is at its peak," the well pump pushed well water into the city supply through an open or leaky valve. EPA's suggested correction: the connection between the well water and city water "should be broken." In the East Bay, EBMUD requires customers with private wells to test a backflow preventer every year, and its FAQ says the requirement holds even when the well serves only irrigation (EBMUD testers).

Property managers: many devices, different clocks

Rules can treat managed landscapes differently from the houses around them. Horseshoe Bay tests HOA and POA systems every year, and Washington lists irrigation with chemical addition at parks, golf courses and cemeteries as high hazard. Where the clock runs 12 months from each device's last test, as in Gahanna, devices tested at different times keep different due dates. Keep a list by serial number and location that matches the utility's records, and book by due date, not by season.

Next step

Find your water utility in the backflow tester directory and book a tester from its list inside your test window. Utility pages include Salt Lake City, whose winterizing sheet is quoted above; Round Rock, with its seven-year residential cycle; Houston; Columbus, which falls under Ohio's rules (the PVB exception for water-only lawn systems is one a water supplier may apply, so ask); and Marin Water in California. If you are adding an injector, a pump or a well connection, ask the utility which device it requires first, then plan the work.

Questions people ask