What is a backflow preventer, and does yours need testing?
A backflow preventer keeps dirty water from flowing backward into your drinking water. Without one, a pressure change can send water carrying fertilizer, pool chemicals, or worse backward into the same pipes that feed your kitchen sink. What needs testing, if anything, depends on what’s connected to your water line and what your water utility requires.
What backflow is
There are two ways it happens. Back-pressure is when something downstream, like a boiler or a fire sprinkler system, runs at higher pressure than the incoming water line and pushes water backward. Backsiphonage is the sneakier one. A sudden pressure drop in the main, maybe from a break or heavy firefighting demand nearby, creates suction that pulls water backward from wherever it’s sitting, including a hose left in a bucket of chemicals or a sprinkler head sitting in standing water.
Where you’ll find a backflow preventer
- Lawn irrigation systems, since a sprinkler head can sit in fertilizer, pesticide, or just standing dirty water
- Fire sprinkler systems, where the water sits still in the pipes for years at a time
- Commercial buildings, especially ones with any kind of industrial process on site
- Boilers, since the water inside picks up treatment chemicals
- Some pools, depending on how they’re filled
A typical house without irrigation or a fire system usually doesn’t have one, other than the small vacuum breaker built into a lot of newer outdoor faucets.
The different types, in plain words
A vacuum breaker is the simplest kind, often built right into an outdoor hose faucet. It keeps a hose sitting in a bucket from siphoning water backward into the house. A pressure vacuum breaker and a double check valve are both common on irrigation systems, doing a similar job with a bit more protection built in. A reduced pressure zone assembly, often just called an RP or RPZ, goes on higher risk connections like fire systems or commercial buildings, and it’s built to handle both back-pressure and backsiphonage at once.
Does yours need to be tested?
Plenty of water utilities require certain backflow devices to be tested on a schedule, often once a year, by a certified tester, and some send a notice when yours is due. Rules vary by utility, so call yours. If you’ve gotten a notice about testing, that’s your utility telling you it applies to your property.
Got a notice about backflow testing? Don’t set it aside. Utilities that require testing generally follow up, and it’s easier to handle now than to sort out a missed deadline later.
What a backflow test involves
A certified tester connects a gauge kit to the device and checks that each internal check valve and relief mechanism is holding pressure and closing the way it’s supposed to. It’s a quick, non-invasive test on most residential and small commercial devices. The tester files a report, usually with the water utility directly, and that report is what shows the device passed.
Protecting an above-ground device in winter
A lot of irrigation backflow devices sit above ground right out in the yard, and even the ones in a valve box can freeze in a hard cold snap. An insulated cover made for the device helps, and some systems have a way to drain the water out of it before a freeze hits. It’s the same thinking as protecting the rest of your outdoor plumbing. Here’s more on keeping pipes from freezing.
Property managers and business owners tend to run into backflow testing more than anyone else, since irrigation, fire sprinklers, and commercial connections are where utilities focus. If you’re managing a property and aren’t sure what’s installed or what it needs, we can take a look and help you figure out what your utility is asking for. More on how we work with property managers here.