How to Test a Backflow Valve

What You'll Need
Water Pressure Gauge

A backflow valve is a device which prevents water from flowing backwards, and should be tested each year in order to ensure that the household is properly defended from contamination and pollution of their drinking after. Backflow prevention valves often have building codes which surround their installation and use, and you may find that it's necessary to test your backflow valve yearly in order to preserve compliance with building regulations. If you have only just moved into a house with a backflow valve, or you have been ordered to test it without knowing how, here are a few simple rules to follow in order to test yours, and to keep you and your household safe.

Step 1 - Locating the Test Valve

All backflow prevention valves which are installed in domestic homes are fitted with a test cock and a shut-off valve, which are necessary to the testing of the valve. Find these parts on the valve by examining your device. The location of the test cock varies between makers, so where your valve is on your product will depend upon the type you have. Some devices, for example, have two test cocks which are Y-shaped, and can be easily located just by looking at the valve.

Step 2 - Opening the Test Cock Valve

Taking your wrench, open the test cock valve. This will involve turning it a one-quarter turn, so that it's at a 90-degree angle from its starting position. Turn on your water, and run a few taps at once. The water should now be trying to flow backwards through the system. Check for two things, by examining whether the relief valve, which is the third valve in your connection opens. Other valves may start to leak, or may seal tightly. You may need to check that the valve is fully closed by pushing at the side with your screwdriver. If it opens, the backflow valve may need replacing.

Step 3 - Checking the Pressure

You should now check the water pressure inside the valve, either by using a pressure gauge which is attached to the valve, or by using one which you have purchased. If the pressure is increasing while the test cock is on, you should consider whether to replace the valve. Check the water pressure in the rest of the house before you take the measurement here, as it will give you a clear idea of whether pressure is rising as the water struggles to move backwards.

Step 4 - Call in a Professional

Strictly speaking, the backflow valve test should be performed by a professional plumber. In most states, it is in fact illegal to not have your valve tested annually by a professional, so you should consider that before attempting to test it for yourself. A professional will be able to examine the valve for small problems that an amateur may miss, and will also be able to test all of the shut-off valves on your system. Professionals may be expensive, but they can save you money through knowing how to treat any problems that arise.