Backflow Prevention

Backflow is when water flows backward through your plumbing — the opposite of its normal direction. When that happens, contaminated water from sources like irrigation systems, boilers, or the ground can be drawn into your clean drinking water supply. Because it's a genuine health risk, most areas require devices to prevent it.

A backflow preventer is a valve or assembly installed on your plumbing that lets water flow one way and blocks it from flowing back. It sits between your clean water supply and any source that could contaminate it. There are several types, from simple check valves to more robust assemblies, depending on the level of risk.

A backflow test checks that your backflow prevention device is working — that it stops water from reversing as designed. Many local water authorities require these tests, often annually, for homes and businesses with irrigation systems, pools, or other cross-connections. A certified plumber performs the test and files the results with your water provider.

Most jurisdictions require testing once a year, though the exact schedule is set by your local water authority. Devices can wear out and fail silently, which is why regular testing is mandated. A certified backflow tester can confirm your local requirement and keep you on schedule.

Backflow testing must be done by a certified tester — usually a licensed plumber who holds a specific backflow certification recognized by your water authority. Not every plumber carries this certification, so it's worth confirming. Profiles in the directory note certifications and specialties so you can find a qualified tester near you.

It depends on your setup and local code. Homes with irrigation systems, swimming pools, boilers, or wells often require one because they create a connection between clean water and a potential contaminant. Your local water authority sets the rules. A certified plumber can tell you whether your property needs a device and which type.

Skipping a required test can lead to notices from your water authority and, in some cases, having your water service interrupted until you comply. More importantly, an untested device may be failing without your knowledge, leaving your drinking water at risk. Staying on the annual schedule keeps you compliant and safe.

A cross-connection is any point where your clean drinking water could come into contact with a source of contamination — like a hose left in a bucket, an irrigation line, or a boiler. Backflow preventers are installed at these points to keep the two water sources separate. A plumber can identify cross-connections in your home during an inspection.

It can, which is why irrigation systems are one of the most common reasons homes need a backflow preventer. Fertilizers, pesticides, and ground contaminants near sprinkler heads could be siphoned back into your drinking water if pressure drops. A certified plumber can install and test the right device for your irrigation setup.

Watch for water discoloration, an unusual taste or smell, reduced water pressure, water leaking from the device, or spitting and dripping at the assembly. Since some failures aren't obvious, annual testing is the reliable way to catch problems. If you notice any of these signs, contact a certified plumber to inspect the device.

No — testing requires certification and specialized gauges, and repairs must keep the device compliant with code and your water authority's rules. This isn't a DIY job. A certified backflow plumber has the training and equipment to test, repair, or rebuild the assembly correctly and file the paperwork.

Keep the assembly accessible and protected from freezing, since cold weather can crack the valves, and don't cover it up with landscaping or structures. Schedule your required annual test and address any repairs promptly. A certified plumber can insulate the device for winter and advise on protecting it year-round.

Yes. Above-ground backflow assemblies are exposed and can freeze and crack in cold weather, causing leaks and failures. In colder climates, many homeowners insulate the device or have irrigation lines winterized before the first freeze. A local plumber can recommend the right protection for your area.

The main types range from simple check valves and pressure vacuum breakers to more protective double-check and reduced-pressure zone assemblies. The right one depends on how much of a contamination risk the connection poses — higher-risk situations require stronger protection. Your local code and a certified plumber determine which type your property needs.

Often, yes. Commercial properties, restaurants, medical facilities, and buildings with complex plumbing usually face more rigorous backflow requirements and more frequent testing because the contamination risks are greater. Requirements are set by your local water authority. A certified plumber experienced in commercial work can help a business stay compliant.

Look for a licensed plumber who holds a current backflow certification recognized by your water authority and has experience with testing and installation. Check that they can file test results on your behalf. The directory lets you compare certified backflow pros near you by specialty, service area, and reviews.

A certified tester attaches gauges to your device, temporarily shuts off the water, and measures whether the valves hold pressure and block reverse flow as designed. The test is quick and the water is off only briefly. Afterward, the tester documents the results and submits them to your water authority to keep you compliant.