How Often Is Backflow Testing Required?

The short answer is once per year. California requires annual backflow testing for every device connected to the public water supply. But the exact timing, process, and consequences vary by water district. If you are in the South Bay, here is what you need to know about the schedule and how to stay ahead of it.

State Law vs. Local District Rules

California Health and Safety Code Section 116875 requires annual testing of all backflow prevention devices. However, the actual enforcement, scheduling, and record-keeping are handled by your local water district. In the South Bay, that means one of the following districts: San Jose Water Company, Santa Clara Valley Water District, California Water Service, or the City of Sunnyvale Water Department. Each district has its own notice cycle, but the legal requirement is the same: test once every 12 months.

When the Testing Year Starts

Most districts base your testing year on the date of your last successful test. If you tested in March 2026, your next test is due by March 2027. Some districts send notices 30 to 60 days before the deadline. Others send a single notice with a fixed deadline, regardless of when you tested last year. The safest approach is to schedule your test roughly 11 months after the last one. This gives you a buffer and avoids the last-minute rush when every tester is booked solid.

Are There Any Exceptions

There are very few exceptions. A device must be tested annually even if it was recently installed or repaired. Newly installed devices require an initial test to confirm correct installation. Repaired devices require a retest to confirm the repair was successful. The only exception is if the device is permanently removed from service and the water district officially removes it from your registry. Even then, you must prove the cross-connection hazard no longer exists.

What Happens If You Miss the Deadline

• Second notice: Most districts send a reminder within 30 days of the missed deadline.
• Late fees: Administrative fees of $50 to $150 are common after the first notice.
• Compliance flag: Non-compliance may be recorded on your property record.
• Water service risk: For commercial properties, the district may restrict service. For residential, this is rare but possible after repeated non-compliance.

How to Stay on Track

Set a calendar reminder 11 months after your last test. Keep a digital or physical folder with every test report. If you buy a new property, ask the seller for the last test report. If the device has not been tested in over a year, schedule one immediately. The district may already have a notice in the mail. The best way to avoid stress is to test proactively, not reactively.

Bottom Line

Backflow testing is required every 12 months in California. No exceptions, no extensions, and no shortcuts. The cost is low, the test is quick, and the peace of mind is worth it. Set a reminder, keep your reports, and schedule early. South Bay water districts take compliance seriously, and so should you.