Think of it as your building's annual physical, except the law actually requires this one.
Normally, clean water flows one direction, from the city main into your building. But when pressure drops or reverses (a water-main break, a hydrant opening, a pump kicking on), water can get pulled backward. If that backward flow carries irrigation runoff, fire-system water, or chemicals into the public supply, it's a contamination risk for everyone on the line.
A backflow prevention assembly is a one-way gate that keeps contaminated water from ever flowing back. But it has internal parts (checks, springs, relief valves) that wear out silently. The only way to know it still works is to test it. That's why California Title 17 and your local water purveyor require a certified test every year.
Miss the annual deadline and your water district will notice. Typically you'll get a reminder, then a more pointed notice, then (for stubborn cases) fees or even a water-service shutoff until you're compliant. None of it is dramatic if you stay ahead of it, which is the entire point of getting matched with a tester who tracks the date for you.
Get matched with a certified tester who handles the test and the filing, every year.
Find a certified tester →Free and quick
A certified, county-registered tester for your ZIP and assembly, usually within one business day. Check your email (including spam) for the intro.