Failed backflow test: what failed, your repair deadline, and when to replace the device

The short answer: a failed backflow test means at least one part of the assembly, a check valve, the relief valve or the air inlet, missed its pass line when the tester put a gauge on it. By itself, a failed reading does not show that backflow happened. It does start a clock. California's state handbook gives 30 days from notification of the failure to repair or replace the assembly. Round Rock, Texas, Athens-Clarke County, Georgia, and Manatee County, Florida, also give 30 days. One Colorado district gives 60. Then the assembly has to pass a retest, and the passing report has to reach the utility. The fix is usually smaller than owners fear: one Florida city's fact sheet says a failed assembly often only needs to be cleaned.

Gauge readings and pass lines are in how backflow testing works; prices are in the backflow testing cost guide. Each rule below is quoted from the state or utility that set it, and your own notice has the final word.

What "failed" means on your report

The test checks each part of the assembly separately, so the report tells you which one failed, and each kind of failure points to a different likely cause. Texas' Form TCEQ-20700, for example, has a box for each reading on the initial test, a row for "Repairs and Materials Used," and a row for the "Test After Repair."

The U.S. Environmental Protection Agency's Cross-Connection Control Manual explains the usual causes. On the reduced pressure (RP) assembly: "If water exits the relief valve, in all likelihood, the first check valve is fouled and it is impractical to proceed with the testing until the valve is serviced." On check valves in general: "all valves may leak as a result of wear or obstruction."

Sources: EPA Cross-Connection Control Manual (2003); Wilton Manors, FL, fact sheet (updated 04-09-24); Southington, CT, FAQ; Salt Lake City winterizing guide. Your tester's findings come first.

The USC Foundation for Cross-Connection Control and Hydraulic Research (USC FCCCHR), whose manual the state rules point to, wrote in 1994 that failing a field test "does not directly correlate" with backflow happening; a failure means the assembly "may need repair." Your utility still treats it as a failure.

Why assemblies fail: the causes the sources name

The causes in official sources come down to dirt, wear, idleness and frost.

Debris from the water main

Check valves seal rubber against a seat, and grit keeps them from closing tight. The EPA manual says the spring loading on a double check's valves lets them "'bite' through small debris and still seal." Its model cross-connection program for water departments says main repairs, main breaks, fires and the "periodic cleaning and flushing of mains" may "'stir up' debris within the water main that will cause fouling of backflow devices installed without the benefit of strainers," and "strongly recommends" strainers immediately upstream on new retrofit installations of RP and double check assemblies.

Worn rubber parts and springs

"Backflow prevention assemblies are mechanical devices that have moving parts that can wear out and fail," says the City of Sacramento. Southington's water department says a backflow preventer "is prone to wear and tear." One utility in our directory turns this into a rule: the Athens-Clarke County Cross Connection Control Manual says "All rubber parts shall be replaced at no less than five (5) year intervals," whether or not the device fails.

Devices that sit idle

Southington's FAQ says backflow preventers "that do not have water turned on to them for a long period of time are more prone to failures." That is common on irrigation systems that stay off most of the year. Seasonal shutdowns and testing are covered in our irrigation backflow testing guide.

Freezing

Colorado State University Extension says backflow prevention devices "will be damaged by freezing during the winter unless they are drained of all water." Salt Lake City's guide adds that frozen water in the device or its ball valves "can cause internal damage or possible crack the device or valve."

How often assemblies fail: one city's numbers

In the one set of local numbers we could check, failure was the exception. Oregon Health Authority's Drinking Water Services collects a yearly cross-connection Annual Summary Report from water systems, with counts of assemblies tested, passed and failed by type. The City of Wilsonville's 2024 report is one example. The table gives its counts as printed; the chart shows the share of tested assemblies that failed, which we computed from those counts.

Source: Wilsonville 2024 Annual Summary Report to the Oregon Health Authority, questions 10 to 12 (Internet Archive copy, captured January 18, 2026).

That is one city's year, not a national rate, and the PVB figure rests on only 35 tests. Still, most tested assemblies passed.

Your deadline: what each rule says

No national rule sets the repair time. Some state rules set a number; others leave it to the utility.

Several utilities in our directory, among them EBMUD, Marin Water and Sacramento, do not print a repair window on their program pages. They are California public water systems, and the state handbook puts the 30-day duty on them. Their plans may allow extensions; ask before you need one.

For Ohio utilities such as Columbus, the state rule gives no number, so the deadline is the one printed on the utility's notice. Ask the office named on the letter if it is not printed.

The retest and the paperwork

The repair is half the job. The other half is a passing test on file at the utility.

• One form or two. TCEQ's form puts the initial test, the repairs and the "Test After Repair" on one sheet when the same licensed tester does all of it. "Any follow-up testing performed by a different tester must be documented on a separate form." If you change testers after a failure, expect two reports.
• Parts on order. Utilities disagree on what the tester does while waiting. Corpus Christi wants the failed report filed within 10 calendar days and a separate report when the device passes. Galveston asks testers to wait and enter both tests in one report, which "will keep us from sending letters for a failed test unnecessarily to the customer." Ask your tester which way your utility works.
• Parts must match. TCEQ's form says: "USE ONLY MANUFACTURER'S REPLACEMENT PARTS." California says approved assemblies "must not be modified."
• Keep your copy. Ohio puts record-keeping on the property owner, and Irving requires testers to give the customer "A copy of the backflow test form (not just the invoice)."

Repair or replace?

The sources lean firmly toward repair. The City of Wilton Manors, Florida, tells owners that approved assemblies "are designed to last from 20 to 50 years" and "should not be replaced unless parts are no longer available or if the assembly has sustained damage to the body." For assemblies 2 inches and smaller, it says, the initial test, a cleaning, new rubber parts and a final test "can be accomplished in one hour."

Four triggers for replacement recur in the sources:

1. No parts. Washington requires an unlisted assembly to be replaced by an approved one when it "Cannot be repaired using spare parts from the original manufacturer." EBMUD says devices installed earlier with its approval "may continue to be tested until such time as they are no longer repairable and then will be required to upgrade to current standards."
2. Damage to the body. Wilton Manors names body damage as a reason to replace, and freezing is one way bodies crack (Salt Lake City, CSU Extension).
3. The wrong device for the hazard. Washington's rule puts assemblies "not commensurate with the degree of hazard" on the same footing as failing ones; a repair cannot turn the wrong device into the right one. In California, "Sites with an auxiliary water supply" are on the handbook's list of high-hazard premises that need an air gap or an RP, and EBMUD names "a well or source of auxiliary water" among the conditions that may call for a device. The handbook's note on that line lets an existing double check installed before July 1, 2024, stay only if, among other conditions, it "passes all field tests in the assembly testing and repair timeframe" in the utility's plan, and adds: "An AG, RP, or both is required for all new or replacement assembly installations after July 1, 2024." The handbook does not name private wells, and the same appendix lets a water system "reduce or increase the minimum protection required" after a hazard reassessment. So if your California property has a well and its old double check has to be replaced, ask the water system before ordering whether the replacement must be an RP or an air gap, as that note points to.
4. Moving it. Washington requires an unlisted assembly to be replaced if it "Is moved." California, Washington and Houston also require a test after relocation.

When you replace, the new device has to meet today's rules, not the ones in force when the old one went in. Ohio says that when containment backflow preventers are replaced, the new ones must meet the rule's current requirements "at the time of installation." California requires each replaced or newly installed PVB, SVB, double check and RP to be approved under the USC FCCCHR Tenth Edition standards or the ASSE standards it lists with "the 1YT mark." It also requires a replaced RP to sit at least 12 inches and, unless the water system approves otherwise, no more than 36 inches above grade. Double checks installed or replaced since the handbook's adoption follow the same rule unless the water system finds no alternative, so an old double check in a pit may have to come up into the air.

Replacement also brings paperwork. Irving tells testers that "Verification of a plumbing permit is necessary for any newly replaced or installed assembly before testing," and wants the old serial number on the report. Houston asks owners to have their plumber, engineer or testing company email it a Backflow Prevention Assembly Removal Form where an assembly has been replaced, removed or duplicated. A replacement also needs its own passing test: California requires it after installation, as do Houston and Washington.

Decision table

Who may do the repair

Being allowed to test is not always being allowed to repair; inside a building, plumbing licensing can decide it.

• Texas. State rules say licensed backflow prevention assembly testers "are qualified to test and repair assemblies on any domestic, commercial, industrial, or irrigation service." Fire lines are the exception: testers may work on them "only if they are permanently employed by an Approved Fireline Contractor" (30 TAC 290.44(h)(4)). Houston, Round Rock and Galveston are all under this rule; see the Texas tester lists.
• Washington. The Department of Health's requirements sheet (331-680, November 5, 2021) says testing needs a DOH backflow assembly tester (BAT) certificate. Repair inside a home needs plumbing contractor registration and a PL01, PL02 or PL30 plumber certificate (PL01 or PL30 in commercial buildings); outside buildings, contractor registration under RCW 18.27 or 18.106. State law says testers "who maintain or repair backflow assemblies, devices, or air gaps inside a building are subject to certification under chapter 18.106 RCW" (RCW 70A.120.170).
• Athens-Clarke County, Georgia. Its manual says assemblies "are to be installed by a licensed plumber and repairs made by a licensed Master Plumber." See the Athens-Clarke list.
• California. Marin Water's tester list warns that "State law requires that any plumbing work exceeding $500 must be completed by a licensed contractor," and marks the testers who hold a contractor license. The Contractors State License Board's bulletin of December 31, 2024, says the minor-work exemption rose from $500 to $1,000 on January 1, 2025, "but there is a catch: the work cannot require a permit," and the unlicensed person cannot employ anyone. A repair that needs a permit needs a licensed contractor whatever it costs. A replacement in a city that requires a permit falls in that group.
• Southington, Connecticut. The utility does the testing itself but "will not repair any failed device"; having it repaired is the homeowner's job.
• Ohio. The state rule makes repair the consumer's expense but does not say who may do it. Ask your water supplier before hiring.

Whoever repairs, the retest has to come from a tester your utility accepts, which is why our backflow tester directory copies each utility's own list. Holland, Michigan, for example, says testing there "must be performed by a Plumbing or Mechanical Contractor who is certified by the State Plumbing Board."

If the deadline passes

California requires each public water system to have legal authority to "deny or discontinue water service," to "install, inspect, field test, and/or maintain" the assembly itself, or to otherwise address a failure to comply. Washington lists "Denying or discontinuing water service" among a purveyor's corrective actions, after notice to "the authority having jurisdiction" except in an emergency.

What that looks like locally:

• The utility does the work and bills you. In Round Rock, a device not tested in the allotted time is tested by the city, and if that test fails, "the actual cost of the repairs and the retest will be applied to the owner's water bill."
• A second, shorter notice, then shut-off. Athens-Clarke County gives "ten (10) days to comply with the notice or the water service will be terminated," and its manual says "a reconnection fee can be established."
• Fines. Houston warns of "citations being issued with fines of up to $2,000 per day and the risk of potential suspension of water services." Copper Mountain lists "Failure to repair or replace a faulty backflow assembly within 60 days" as a violation, says non-compliance "may result in monthly penalty fees of $1000 per violation," and suspends service if the problem is not corrected within 120 days.
• Termination and restoration charges. EBMUD says non-compliance "will result in your water service being discontinued and fines being imposed," and its fee schedule has a $784 charge where service "has been terminated for failure to meet the District's Backflow Program requirements." Marin Water says non-compliance "can result in termination of water service." Beaumont-Cherry Valley Water District lists a $200 "Backflow noncompliance turn off/on" fee for 2026.

More fees are compared in the cost guide.

Worked examples

Each example uses only rules quoted above.

A Round Rock homeowner whose sprinkler PVB fails on the check valve. The city gives 30 days to repair and retest. Texas lets the licensed tester do the repair, so cleaning or new rubber parts and a retest on one visit can close it out, with the report filed online. Decision table row 1.

An EBMUD customer with a private well whose old double check fails, and the parts are no longer made. EBMUD lets older approved devices stay "until such time as they are no longer repairable." This one isn't, so it must be upgraded. EBMUD's page names "a well or source of auxiliary water" together, and the handbook's note on such sites calls for "An AG, RP, or both" in replacement installations, so the owner should ask the district whether the new device must be an RP or an air gap before ordering it. A replaced RP or double check goes at least 12 inches above grade and, unless the district approves otherwise, no more than 36. California's 30-day window applies, so the owner should ask about an extension before ordering the work. Decision table rows 4 and 6.

A Houston restaurant whose RP discharges from the relief valve at the start of the test. The EPA manual points to a fouled first check. The site stays out of compliance "until a passing test report is submitted." If the assembly is on the fire line, the tester must work for an Approved Fireline Contractor. Decision table rows 2 and 8.

Restaurants, commercial buildings and property managers

Keeping water on during repairs. The EPA's model program says parallel installation of two devices "is an effective means of the owner insuring that uninterrupted water service during testing or repair of devices." The same model program says "High hazard situations will not be allowed to continue unprotected if the backflow preventer fails the test and cannot be repaired immediately," and sets 30 days for other situations. That is a model for water departments, not a federal rule.

Next step

Find your utility in the backflow tester directory (or start at the Texas or California lists) and book a tester who can repair and retest before the date on your notice. If the job grows into a replacement, ask the utility about the permit and the deadline on the same call. Once the passing report is filed, ask the utility to confirm it has it.

Questions people ask