What backflow is and why it matters
Under normal conditions, water flows from the public main into your building and out through fixtures. Backflow occurs when that flow reverses. It can happen through backpressure, when pressure inside a building's system exceeds supply pressure, or through backsiphonage, when a drop in supply pressure, such as during a water main break or firefighting, draws water backward from the building into the public supply.
When backflow occurs at a connection where water contacts contaminants, those contaminants can enter the drinking water system. Irrigation systems can carry fertilizers and pesticides. Boilers can carry treatment chemicals. Commercial kitchens, medical offices, car washes and manufacturing processes all involve water that should never return to the public supply.
Backflow prevention assemblies are installed at these cross-connections to stop reverse flow. They use check valves, relief valves and air gaps to ensure water only moves in one direction. Like any mechanical device, they wear over time, which is why regular testing is required to confirm they still work.
Testing requirements are set by local water authorities, and many require testing at least annually, along with testing after installation or repair. Commercial properties often have several assemblies, including on fire sprinkler lines, and our Commercial Plumbing Repair team handles related repairs and replacements.
Situations that require backflow testing
If any of these apply, check your water authority's requirements or call us to confirm.
- You received a testing noticeWater authorities typically send notices when a test is due. Missing the deadline can lead to fines or service interruption.
- Lawn irrigation systemIrrigation systems connected to the potable supply usually require a backflow preventer and periodic testing.
- Commercial or industrial propertyRestaurants, medical offices, laundries and many other businesses have cross-connections that require protection.
- Fire sprinkler systemFire protection systems often include backflow assemblies that must be tested on a set schedule.
- New installation or relocationNewly installed or moved assemblies typically must be tested before being placed in service.
- After repairs to the assemblyAny repair or rebuild generally requires a retest to confirm proper operation.
Backflow test due?
Call to schedule testing. We handle the test, any repairs and the paperwork your water authority requires.
How backflow testing works
A standard test on an accessible assembly usually takes under an hour.
Scheduling and notification
We schedule the test and let you know if water service will be briefly interrupted during testing.
Visual inspection
The assembly is inspected for leaks, damage, freeze protection and proper installation, including clearance and orientation.
Test procedure
Using a calibrated test kit, we check the check valves, relief valve and shutoff valves against the pressure standards for that assembly type.
Repairs if needed
If the assembly fails, we explain why and, with your approval, repair or rebuild it with manufacturer parts, then retest.
Reporting
Test results are documented on the forms required by your water authority and submitted according to their procedures, with a copy provided to you.
Common assembly types and their differences
Double check valve assemblies use two independent check valves and are used for lower-hazard applications, such as many fire sprinkler systems. Reduced pressure zone assemblies add a relief valve between the checks and are required for higher-hazard applications because they discharge water rather than allowing backflow if the checks fail.
Pressure vacuum breakers are common on residential irrigation systems and protect against backsiphonage. Each assembly type has its own test procedure, installation requirements and typical failure points. The type installed on your property depends on the hazard level of the connection and local code requirements.
Why assemblies fail tests
Most test failures come from debris, wear or mineral buildup. Sand, scale and small particles from water mains can lodge in check valve seats, preventing them from closing tightly. Rubber components such as diaphragms, seals and discs harden and crack over time. Springs weaken. Relief valves on reduced pressure zone assemblies can stick or leak.
Repairs usually involve cleaning and replacing internal parts with a manufacturer repair kit. When an assembly is badly corroded, damaged by freezing or no longer supported by parts availability, replacement may be recommended. We explain the options and costs before proceeding.
Freeze protection for outdoor assemblies
Backflow assemblies installed outdoors, particularly on irrigation systems, are vulnerable to freezing. Water trapped inside can expand and crack the body or internal components, causing leaks and test failures. Irrigation systems in cold climates should be winterized, and assemblies may need to be drained or protected with insulated enclosures.
If an assembly has been damaged by freezing, it may need repair or replacement before it can pass a test. Protecting exposed plumbing from freezing is a broader concern, and our Frozen Pipe Repair page describes steps to protect other vulnerable pipes during cold weather.
Keeping records and staying compliant
Water authorities maintain records of backflow assemblies within their service area and track testing compliance. Property owners are typically responsible for ensuring tests are completed and reported on time. Missing a test can lead to warning notices, fines and, in some jurisdictions, suspension of water service until compliance is restored.
We keep records of the assemblies we test and can remind you when testing is due. For property managers with multiple sites, organized testing schedules and consolidated reporting help keep every assembly compliant without last-minute scrambles.
Installation details that affect testing
How an assembly is installed determines whether it can be tested easily and whether it will keep working. Assemblies need enough clearance around them for a tester to connect gauges and operate the test cocks. Reduced pressure zone assemblies discharge water through their relief valve when they detect a problem, so they must be installed where that discharge can drain safely, never in a pit or location where the relief port could be submerged.
Assemblies installed indoors should have a drain nearby for the same reason. When an existing assembly is poorly located, testing can still be performed, but relocation may be recommended to meet current code and make future testing and repairs simpler. We point out these issues during the visual inspection so you can plan any changes.
Backflow testing questions
Many water authorities require testing at least once a year, as well as after installation or repair. Some high-hazard connections may require more frequent testing. Your water authority's notice specifies the requirements.
Water to the protected system is typically interrupted briefly during testing. For most properties, the interruption is short. We coordinate timing with you in advance.
The assembly needs repair or replacement, followed by a retest. We can usually repair common failures on the same visit if parts are available.
In most areas, the property owner is responsible for ensuring assemblies are tested and results reported. Tenants and property managers should check lease terms and local rules.
Some do, particularly those with irrigation systems, fire sprinklers, boilers or other cross-connections. Requirements vary by water authority.
Services that support backflow compliance
Repairs, winter protection and commercial services connect to backflow compliance.