Backflow occurs when water is drawn back into your main water supply from another source. The water entering the drinking water system may be contaminated, and will remain in water lines until it is drained from another fixture in your home or your neighbors. A serious health hazard could result when this contaminated water is used for drinking, cooking or bathing. Locations in your plumbing system where backflow can potentially occur are called cross connections. Some examples of cross connections include: hose connections to chemical solutions for herbicides, pesticides, or fertilizers. Lawn irrigation systems, water softeners, hose connections to a laundry tub, a pets water bowl, swimming pools, hot tubs, lake intake structures or any connection that has water are also examples of cross connections.
How does backflow occur?
Backflow is caused by either backsiphonage or backpressure. Backsiphonage occurs when a vacuum is induced on a piping system, just like drinking from a glass with a straw. Any hose can act as a “straw,” allowing undesirable liquids to be drawn through it. Back pressure occurs due to a drop in pressure from the water system. It is important to note that a drop in pressure is out of your control and can occur at any time. Just think that the hose you just left in the horse or dogs water bowl could be the straw that sucks that water directly into your faucet. You may be drinking the same water as your neighbor. We are all connected either through an aquifer or direct piping.
What should you do?
Installation of backflow devices will protect potable water supplies from contamination due to backflow. Generally, city ordinances require backflow preventers to be installed where cross connections may occur. These devices must be tested annually to ensure they are functioning properly. In places where installation and testing of mechanical backflow preventers is not possible, an air gap separation is usually required. Historically, cross connections have been one of the most serious public health threats. It is possible to siphon your neighbors whole duck pond back into a public drinking water supply and then send it to your community.