Backflow Testing & Prevention in Denton, TX
A notice from the city says your backflow assembly is due. Or a new sprinkler system needs one installed. Backflow testing and prevention in Denton, TX covers the yearly test, repairs to assemblies that fail and new installations.
Got a backflow test notice from the city?
That letter or email is why most homeowners first hear the word. A backflow prevention assembly is a set of check valves that lets water flow only one way, from the city system into your property. It stops water from your irrigation system or a commercial process from being siphoned back into the drinking water supply.
According to the City of Denton, homes with irrigation systems have at least one testable assembly on the irrigation line, and assemblies need testing at least once a year because their mechanical parts can wear or fail. The city says it tracks yearly tests on more than 6,500 commercial assemblies.
The rules come from Chapter 26 of the City of Denton Code of Ordinances, in its cross-connection control and backflow prevention article. The City Council adopted an updated ordinance on March 24, 2026, so it is worth rereading your notice even if you have tested before.
What to do before the tester arrives
A little preparation keeps the visit short.
- Have the city notice handy, since it lists the assembly and the reporting details.
- Open any locked gate and clear plants or mulch away from the assembly or its box.
- Turn the irrigation controller off so zones do not start during the test.
- Let the household know water will be off briefly while the gauge is connected.
How a backflow test works
A standard test takes well under an hour on a residential irrigation assembly.
- The tester locates the assembly, usually near the meter or where the irrigation line leaves the house supply.
- Water is shut off briefly and a calibrated differential pressure gauge is connected to the test cocks.
- Each check valve and relief valve is tested against the required pressure differentials.
- Results are recorded and submitted to the city's reporting system.
- If the assembly fails, the tester explains which part failed and what the repair involves.
Common assembly types
The type on your property decides how it is tested and what fails.
| Assembly | Where you see it | Common failure |
|---|---|---|
| Pressure vacuum breaker (PVB). | Residential irrigation, above ground. | Worn poppet or bonnet seal. Freeze damage. |
| Double check valve assembly. | Irrigation and some commercial lines, often in a box. | Fouled check valves. |
| Reduced pressure zone (RPZ). | Higher-hazard commercial connections. | Relief valve discharging from debris or worn seals. |
Repairs, freezes and irrigation leaks
A failed test usually means a worn rubber part or debris on a check valve seat. Most repairs are rebuild kits, and the assembly is retested after the repair.
Freezes are the other big cause of damage. An above-ground pressure vacuum breaker left full during a hard freeze can crack its body or bonnet. Insulating covers help. Draining the irrigation system before a forecast freeze helps more.
A backflow assembly that leaks can also look like a high water bill mystery. Our guide to tracking down where the water goes explains how irrigation leaks get separated from house leaks. Businesses with several assemblies can book all their devices in one visit.
Installing a new assembly
New sprinkler systems need a backflow assembly before they are hooked up. Texas requires an approved assembly on any sprinkler system tied to city water. The City of Denton also wants new ones tested when they go in.
Placement matters. An above-ground pressure vacuum breaker has to sit higher than the highest sprinkler head it serves, or it cannot do its job. A double check assembly in a buried box needs room around it for testing and repair.
When an old assembly fails its test more than once, or the body has cracked from a freeze, replacement is often cheaper than repeated rebuilds. The new unit is tested on installation and the results go to the city's reporting system.
Moving or removing an assembly also has rules. The city expects to know about any change, so do not pull one out during a yard project without checking first.
What backflow testing and repair cost depend on
Testing prices are usually straightforward. Repairs vary.
- Number and type of assemblies on the property.
- Access. Assemblies buried in boxes or behind landscaping take longer.
- Repair kit or replacement if the assembly fails.
- Freeze damage, which can require a new assembly.
Ask whether the price includes submitting results to the city. It should.
Backflow questions
The city tracks late tests and follows up. Keeping your water service can depend on getting the test done, so book it before the date on the notice.
A tester licensed by the state environmental agency, the TCEQ, runs the test with a calibrated gauge.
Most homes without irrigation, fire sprinklers or special equipment do not have a testable assembly. Fixtures like toilets and faucets have built-in protection.
Yes, in nearby towns such as Aubrey. Each city runs its own reporting program, so bring the notice from yours.
Denton Apex Plumbing coverage map
Coverage map for Denton and the nearby Denton County towns we serve.