Backflow Preventer Testing: Does the Water Really Need to Be Off?

Your backflow preventer is a silent guardian, diligently protecting your drinking water from contamination. But like any safety device, it needs regular testing to ensure it's working correctly. A common question homeowners and property managers ask is: Can a backflow preventer be tested without shutting off the water supply?

Let's dive into what you need to know.

The Short Answer: Usually, Yes, the Water Needs to Be Off

For the vast majority of common testable backflow prevention assemblies – such as Reduced Pressure Zone (RPZ), Double Check Valve Assembly (DCVA), and Pressure Vacuum Breaker (PVB) devices – the answer is yes, the water supply to the device must be temporarily shut off during the testing procedure.

Why the Water Shut-Off is Necessary

Backflow preventer testing isn't just a visual inspection. It involves a certified tester using specialized differential pressure gauge equipment to:

1. Isolate the Device: The tester needs to stop the normal flow of water through the preventer. This is typically done by closing the shut-off valves on either side of the device.

2. Test Internal Components: The tester checks the functionality of the internal check valves and, in the case of an RPZ, the relief valve. They are looking to see if these components:

   • Hold the required pressure.

   • Prevent water from flowing backward.

   • Open and discharge correctly (for RPZ relief valves) under specific test conditions.

3. Simulate Backflow Conditions: Part of the test involves creating conditions that would occur during a backflow event to ensure the device responds appropriately.

To accurately assess these critical functions, the normal water pressure and flow through the device must be stopped. If water were still flowing, it would be impossible to get accurate readings and verify that the internal mechanisms are sealing and operating as designed.

How Long is the Water Off?

The good news is that for a routine backflow test, the water shut-off is usually quite brief. A skilled, certified tester can typically complete the test within 15 to 30 minutes, minimizing any inconvenience.

Are There Any Exceptions?

While some highly specialized or complex industrial systems might have bypass loops or redundant systems allowing for testing without a complete shutdown of the main supply, this is not the case for standard residential or commercial backflow preventers found on irrigation systems or main water lines.

For these, a temporary interruption of the water supply through the device is standard operating procedure for accurate testing.

The Importance of Professional, Certified Testing

Attempting to test a backflow preventer without proper training and equipment, or without shutting off the water, will not yield valid results and could even damage the device. More importantly, it won't satisfy legal requirements for annual testing, which are in place to protect public health.Always hire a certified backflow tester.

They have the knowledge, specialized tools, and understanding of local regulations to perform the test correctly and ensure your water supply remains safe.

In Conclusion

While a brief water interruption might seem like a minor inconvenience, it's a crucial step in the backflow preventer testing process. This temporary shut-off allows certified professionals to accurately verify that your device is functioning correctly, safeguarding your potable water from harmful contaminants. Regular, professional testing is a small price to pay for peace of mind and compliance with water safety regulations.