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Cross Connection and Backflow Preventors

Cross connection occurs anytime there is connection, either temporary or permanent, between the city water supply and a potentially hazardous water supply on the side of the homeowner, which allows contaminated water to flow back into the water supply. This happens more often with underground landscape irrigation systems and fertilizer spray applicators that are connected to garden hoses.

The backward movement of water or “backflow” can occur by siphoning or back pressure. For example, if a spray nozzle which can be shut off with a valve is used on the end of the garden hose, and that valve is closed but the faucet is left open, the pressure in the hose will reach equilibrium with the water supply pressure, and the hose will expand in response to the supply pressure. However, a sudden large water usage in the house or at another location can cause the supply pressure to drop. This will cause the hose to contract, forcing water from the hose back into the city water supply. Pressure can also build up in a pressurized hose if air is trapped in the hose and then expands as it heats in the sun. This pressure buildup can force water from the hose backwards into the water supply pipe lines.

For that reason, most hosebibs are fitted with backflow preventors. Hose connection vacuum breakers will prevent backflow from occurring from these sources by opening to relieve the pressure build-up as soon as the pressure in the hose becomes greater than the supply pressure. Check to make sure that the backflow preventor is working properly. Be sure that the check valve closes and the atmospheric vent opens whenever the water supply is shut off on your hosebib. It is very simple to do this if a nozzle that can be shut off is used on the end of the hose. With the nozzle shut off, turn on the faucet and allow the hose to pressurize. Then, shut off the faucet while the hose is pressurized. After a few seconds, the hose pressure should be released in a small spray as the atmospheric vent suddenly opens.

Commercial buildings are required to have larger backflow preventors installed on their water systems. There are several types and sizes of backflow preventors used. These backflow preventors must be tested and certified every other year to be sure that they remain working properly.

We can furnish, install, and certify backflow preventors in your home or commercial property.