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Backflow Prevention and Cross Connection

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What do “backflow” and “cross connection” mean?

A cross connection is a connection between a potable drinking water pipe and a non-potable source. For example: you’re planning to spray weed killer on your lawn. You hook up your hose to the faucet on your house and to the sprayer containing the weed killer. If the water pressure drops at the same time you turn on the hose, the pressure change may cause the chemical in the sprayer to be sucked back into your home’s plumbing system through the hose. This is called backflow and could contaminate the water in your home system. Water utilities deal with this issue on a much larger scale – imagine if your hose were connect to a fire hydrant or a public access faucet (e.g. a campground), then the weed killer would be sucked into the public water supply. Backflow from customer service connections is of concern to water utilities, and has been shown to occur in 1.6% of all meter reads and in 5% of homes with backflow-sensing meters. [1] Journal AWWA

Backflow can be prevented by using an attachment on your hose or faucet called a backflow-prevention device. The simplest prevention system is an air gap, which is a physical separation between the pipes. A hose bib vacuum breaker installed on the outdoor spigot will also work. More sophisticated backflow-prevention devices are mandatory for certain industrial and commercial operations, such as dry cleaners and restaurants. Additional information about how you can help to prevent backflow is available in the videos below.

Most water utilities have cross connection control programs, particularly in big cities. Programs include periodic testing of commercial backflow devices by certified technicians. Buildings requiring backflow prevention devices are identified and monitored. Some utility programs also incorporate backflow–sensing meters, which detect residential backflow. Backflow-sensing meters, combined with an effective pressure management program and an automated meter reading system, can provide utilities with near real-time information on backflow events.