A backflow preventer is a valve assembly that keeps water from flowing backward out of your plumbing and into the drinking water supply. Water providers and local authorities often require testable assemblies on irrigation, fire sprinkler and commercial lines, and those assemblies need periodic testing because their internal parts wear over time.
What is backflow, and what does a backflow preventer do?
Backflow is water reversing direction in a pipe. A backflow preventer is a set of check valves that lets water flow one way only, so nothing from your system can be pulled back into the public supply.
Backflow happens two ways. Backsiphonage occurs when pressure in the supply drops, such as during a water main break or heavy firefighting, and water gets sucked backward. Backpressure occurs when pressure on your side, from a pump or a pressurized system, pushes water back toward the main.
The risk comes from cross-connections: any point where drinking water piping connects to something that could contaminate it. Lawn irrigation, fire sprinkler systems, commercial kitchen and beverage equipment and even a garden hose left in a bucket are common examples.
What types of backflow preventers are there?
The type depends on the hazard. Higher-risk connections call for a reduced pressure zone assembly, while lower-risk ones may use a double check valve assembly or a vacuum breaker.
A pressure reducing valve (PRV) is a different device. It lowers incoming water pressure to protect your plumbing, but it does not stop backflow.
- Reduced pressure zone (RPZ) assembly: two check valves with a relief valve between them that dumps water if either check leaks. Used on higher-hazard connections.
- Double check valve assembly: two independent check valves in series. Used on many lower-hazard connections, such as some fire sprinkler lines.
- Pressure vacuum breaker: common on lawn irrigation systems to stop backsiphonage.
- Hose bibb vacuum breaker: a small device on an outdoor faucet that keeps hose water from being siphoned back.
Why does your water provider ask for a backflow test?
Testable assemblies rely on springs, rubber seals and check valves that wear out or get fouled. Many water providers and local authorities require periodic testing by a qualified tester to prove the assembly still works.
During a test, the tester uses a gauge kit connected to the assembly's test cocks to check that each check valve holds and that an RPZ relief valve opens when it should. The results go on a test report that is submitted to whoever requires it. Testing schedules and reporting rules are set locally, so follow the notice from your water provider and confirm requirements with your local building department.
What goes wrong with backflow assemblies?
Debris, worn seals, freezing and age are the usual causes. A failed test does not always mean replacement; many assemblies can be repaired with a parts kit.
- Debris lodged in a check valve so it cannot close fully.
- Worn rubber seals or weak springs that let water pass backward.
- An RPZ relief valve that drips or dumps water, often a sign that a check valve is leaking.
- Freeze damage to above-ground assemblies during Central Arkansas cold snaps.
- Shutoff valves on the assembly that no longer seal, which makes testing and repair harder.
Do you need a permit to install or replace a backflow preventer?
Often, yes. Installing or replacing an assembly is plumbing work that local authorities may regulate. Requirements vary, so confirm with your local building department and water provider.
CASC pulls required permits on the work we do. Our permits guide explains in general terms how permits and inspections work across Central Arkansas cities.
How does CASC handle backflow preventers?
CASC installs, repairs and tests backflow preventers for homes and businesses across Central Arkansas, from irrigation connections to commercial plumbing systems.
Residential visits start with a $99 service call on weekdays or $149 on weekends and holidays. Our technicians are licensed and certified, and the company is fully insured and bonded. Businesses with backflow, grease trap or other commercial plumbing needs can request a quote.
Frequently asked questions
Why did I get a letter asking for a backflow test?
Many water providers keep records of testable backflow assemblies and require periodic testing to confirm they still protect the public water supply. Follow the instructions and deadline in the notice, and call a qualified tester.
My RPZ is dripping water. Is that a problem?
Often, yes. The relief valve discharges when a check valve is not sealing or pressure fluctuates. It should be inspected and repaired so the assembly works as designed.
Is a pressure reducing valve the same as a backflow preventer?
No. A pressure reducing valve lowers incoming water pressure to protect your plumbing. A backflow preventer stops water from flowing backward into the supply.
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Related guides
- Permits and code for HVAC and plumbing work in Central Arkansas Many HVAC and plumbing jobs in Central Arkansas cities, like equipment replacement, water heater swaps, gas line work and sewer line work, commonly need a permit and an inspection. Your city building department issues most permits, state agencies license the trades, and a licensed contractor usually pulls the permit for you.
- How our pricing works Repairs start with a service call: $99 on weekdays and $149 on weekends and holidays, for HVAC and plumbing. That fee is not waived or credited toward the repair. HVAC replacements, larger plumbing projects and commercial HVAC projects get a free estimate instead. There is no travel fee within our normal 50-mile service area.
- Request a commercial HVAC or plumbing quote Businesses can request a commercial HVAC or plumbing quote through our contact form or by calling 501-307-1310. CASC handles rooftop units, split systems and mini-splits, plus commercial plumbing, drains, grease traps and backflow. Commercial HVAC projects get a free estimate, and our quarterly Commercial HVAC Maintenance Program is quoted per building.
- HVAC and plumbing for offices and retail Offices and retail spaces need steady comfort and working restrooms during business hours. Most run rooftop units or split systems, sometimes with mini-splits for server rooms or add-on spaces. Quarterly HVAC maintenance, planned repairs and attention to restrooms, water heaters and backflow devices keep small problems from closing the doors.
Need a backflow test or repair?
Call 501-307-1310 or send a request. Open 7:00 AM to 6:00 PM, seven days a week.
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