Backflow Prevention: Protect Your Drinking Water
Your drinking water flows one way: from the main into your home. Backflow reverses that. A pressure drop in the main, from a water main break or fire hydrant use, can suck water backward out of your home and into the public supply. If that water touched a hose in a pesticide bucket, a boiler, or an irrigation system, contaminants enter the drinking water. Backflow prevention stops this.
What Is Backflow, and Why Does It Matter?
Backflow is water flowing backward into the clean supply. It happens when main pressure drops suddenly or when pressure inside your plumbing exceeds the main. Prevention devices block that reverse flow. A pressure drop in the main, from a water main break or fire hydrant use, can suck water backward out of your home and into the public supply.
If that water touched a hose in a pesticide bucket, a boiler, or an irrigation system, contaminants enter the drinking water. Backflow prevention stops this. It is one of the cheapest forms of protection a home can have, and in many places it is required by law.
The Deston is a nationwide referral service. We connect homeowners across all 50 states with independent local plumbers who install and test backflow prevention devices. We are not a plumbing company. We have no technicians of our own. We match you with a nearby pro who knows your local codes and testing requirements. Many cities require backflow devices on irrigation systems, and some require annual testing with paperwork filed to the water authority. A local pro handles the device, the test, and the forms. One call covers all of it.
Signs You Need Backflow Prevention
You installed a sprinkler system
Most cities require a backflow device on every irrigation connection. Irrigation systems are the most common required location.
You got a notice from the water utility
Letters demanding a device or annual test are common and have deadlines. Your local water authority can confirm the deadline for your property.
You have a boiler or radiant heat
Heating systems need protection so treated water cannot flow backward. Boilers are high-hazard connections that need the strongest devices.
You run a pool fill line
A hose or pipe filling a pool is a classic cross-connection risk. Pool water must never be able to flow back into the clean supply.
You use hose-end sprayers for chemicals
Fertilizer and pesticide sprayers create back-siphonage risk. A hose sitting in a bucket or pool can siphon water backward.
You have a private well plus city water
Dual sources need separation so well water never enters the city main. This is one of the highest-risk setups a home can have.
You are opening a home business
Some commercial uses trigger backflow requirements even in residential zones. If you run a business from home with any commercial water use, ask the pro whether residential rules still apply.
Your annual test is overdue
Lapsed certification can bring fines or a water shutoff notice. Skip the test and the city may fine you or shut off water.
Your device is old or was never tested
Internal springs and seals wear out. A device that looks fine can fail silently. Annual testing catches failure before contamination happens.
Call, Review, Install, Test, File
How a backflow referral usually goes.
- 1
Call The Deston
Dial (888) 418-3086. Tell us about your irrigation, boiler, or the notice you received. One call covers all of it.
- 2
We match you with a local pro
We connect you with an independent plumber near you who installs and tests backflow devices and knows your water authority’s rules.
- 3
Site review
The pro checks where the device must go, what hazard level applies, and which device type your code requires. Device type, location, and access all shape the quote.
- 4
Upfront price
You get a clear quote for the device, installation, and testing before work starts. The local pro quotes everything upfront.
- 5
Installation
The pro installs the device on the line, typically above ground for irrigation with proper drainage and freeze protection. Above-ground devices are vulnerable to freezing, so pros install insulated enclosures or drain the device for winter.
- 6
Testing and paperwork
The pro tests the device with gauges, confirms it holds, and files the certification with your water authority. The certified tester usually files it directly. Confirm this with your pro so nothing slips through the cracks.
Types and Options: RPZ, DCVA, PVB, AVB, and Hose Bib Breakers
Which device you need depends on the hazard level of the connection and what your local code requires. The pro you are matched with picks the right one for your setup.
Reduced pressure zone (RPZ) assemblies
RPZ assemblies offer the highest protection. Two check valves plus a relief valve dump water if either check fails. They suit high-hazard connections like boilers and chemical sprayers. They must drain freely, so placement matters.
Double check valve assemblies (DCVA)
DCVA uses two independent check valves. They protect against backpressure and backsiphonage for moderate hazards like irrigation without chemical injection. Many cities accept them for standard sprinkler systems.
Pressure vacuum breakers (PVB)
PVB is common on residential irrigation. One check valve plus an air inlet breaks siphons. They must sit above the highest sprinkler head and cannot handle backpressure. Simple and affordable.
Atmospheric vacuum breakers (AVB)
AVB is the simplest device. They screw onto hose bibs and irrigation valves. They cannot be under continuous pressure. Cheap and effective for the right spot.
Hose bib vacuum breakers
Hose bib vacuum breakers thread onto outdoor spigots in seconds. They stop a garden hose from siphoning bucket water backward. Every home should have them on every hose bib. Screw-on vacuum breakers are cheap insurance.
Is this the same as a check valve?
A basic check valve is one piece of the puzzle. Code-approved backflow assemblies add test ports, redundant valves, and designs proven to fail safely. A plain check valve does not meet code.
What It Costs
Figures below are national averages for planning. The local pro quotes everything upfront, including the device, installation, and testing.
| Service | Typical national average | Notes |
|---|---|---|
| Residential backflow device install | $300 to $800 | Includes the device and labor |
| RPZ assembly installed | $500 to $1,000 | Device itself costs more |
| Hose bib vacuum breakers | Under $50 installed | Thread onto outdoor spigots in seconds |
| Annual testing | $75 to $200 per device | Required in most areas for RPZ, DCVA, and PVB |
| Repair of a failed device | $150 to $400 | Rebuild kits and labor; most devices can be rebuilt rather than replaced |
| Full replacement of an old failed unit | Approaches new-install pricing | When rebuild is no longer possible |
Before and After: Unprotected Spigot to Certified Assembly
The photos below are illustrations of an unprotected outdoor spigot and a new certified backflow assembly. They show the kind of change to expect, not one specific job.
Before
AfterCommercial Properties Face Stricter Rules
Commercial properties face stricter rules than homes. Restaurants, car washes, and medical offices often need RPZ devices on multiple connections with testing by certified specialists.
Multiple connections
Commercial sites often need RPZ devices on multiple connections, each with its own testing and filing. The pro maps every connection and its hazard level.
Do: ask the pro to list every required device before work starts.
Certified testing
Testing must be done by a certified specialist in most areas. Annual testing is required in most areas for RPZ, DCVA, and PVB devices.
Do: confirm the tester files the report with the water authority.
Forced shutdown risk
Getting this wrong can mean a forced shutdown of your water service until the right device is installed and certified. Lapsed certification can bring fines or a water shutoff notice.
Do: never let a test lapse; set a yearly reminder.
Home businesses
If you run a business from home with any commercial water use, ask the pro whether residential rules still apply. Some commercial uses trigger backflow requirements even in residential zones.
Do: describe every water use on the property to the pro.
Can the Device Freeze in Winter?
Yes, above-ground devices are vulnerable. Pros install insulated enclosures or drain the device for winter. Freeze damage is a top cause of spring failures.
Ask about an insulated enclosure. In cold climates, freeze-protection enclosures are part of the install. They are cheaper than a spring replacement.
Drain the device for winter. If your pro drains the device for winter, confirm who reopens it in spring and whether that visit includes a test.
Test after any freeze. A device that froze may look fine and fail silently. Annual testing catches failure before contamination happens.
Watch for spring failures. Freeze damage is a top cause of spring failures. If your first spring test fails, the tester rebuilds it with new internal parts and retests.
Keep the test on schedule. Most water authorities require the report. A failed test means the device needs repair or replacement right away.
Backflow Prevention FAQs
What exactly is backflow?
Backflow is water flowing backward into the clean supply. It happens when main pressure drops suddenly or when pressure inside your plumbing exceeds the main. Prevention devices block that reverse flow.
Do I really need a device for my sprinklers?
In most cities, yes. Irrigation systems are the most common required location. Check your water bill insert or city website, or ask the pro we connect you with.
Why does my device need testing every year?
Internal springs and seals wear out. A device that looks fine can fail silently. Annual testing catches failure before contamination happens. Most water authorities require the report.
What happens if my device fails the test?
The tester rebuilds it with new internal parts and retests. Most devices can be rebuilt rather than replaced. You get a passing report to file.
Can the device freeze in winter?
Yes, above-ground devices are vulnerable. Pros install insulated enclosures or drain the device for winter. Freeze damage is a top cause of spring failures.
Is this the same as a check valve?
A basic check valve is one piece of the puzzle. Code-approved backflow assemblies add test ports, redundant valves, and designs proven to fail safely. A plain check valve does not meet code.
Who files the paperwork?
The certified tester usually files it directly with your water authority. Confirm this with your pro so nothing slips through the cracks.
Do hose bibs need protection too?
Yes. A hose sitting in a bucket or pool can siphon water backward. Screw-on vacuum breakers are cheap insurance. Every home should have them on every hose bib.
What if my irrigation also needs work?
If your irrigation also needs work, tell the pro during the site review. The pro checks where the device must go, what hazard level applies, and which device type your code requires, and can quote related irrigation work at the same visit.
What happens if my annual test is overdue?
Lapsed certification can bring fines or a water shutoff notice. Many cities require backflow testing every year. The Deston connects you with plumbers who handle testing, paperwork, and any needed fixes in one visit.
Which device does my home need?
That depends on the hazard level of the connection and what your local code requires. RPZ suits high-hazard connections like boilers and chemical sprayers. DCVA suits moderate hazards like irrigation without chemical injection. PVB suits residential irrigation. Your matched pro picks the right one.
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Backflow Protection Is Cheap Insurance for Your Drinking Water.
Call and we will match you with a local pro who installs, tests, and certifies backflow devices, and files the paperwork with your water authority.
(888) 418-3086 Call NowThe Deston is a referral service that connects homeowners with independent local plumbers. We are not a plumbing company.