Cross-Connections at Home

What is a cross-connection?

A cross-connection is a direct link between a household water line and a contaminated source such as a garden hose and a sprayer. The most common contaminants- such as pesticides and detergents- can enter your drinking water through cross-connections in your home water lines.

Back siphonage-

Most household cross-connections are created by hoses. Under certain conditions, the flow in household water lines can reverse and siphon contaminants in the water lines.

For example, using a garden hose to spray pesticides is usually harmless, but if the water pressure is reduced due to a water main break, a back siphonage effect is created. This can draw water from your garden hose into your home water lines; therefore, these chemicals could contaminate your home water supply.

Back pressure-

Your drinking water can also be contaminated by an effect called back pressure. Back pressure occurs when your water supply is connected to a system under high pressure such as a hot water boiler for home heating or a portable pressure washer. Since the pressure in these devices is higher than your home water supply, water can sometimes be forced backwards. Contaminants-such as cleaners and soaps-could enter your home water system.


Prevent back siphonage and back pressure by using an inexpensive, easy-to-install hose connection vacuum breaker. This one-way valve allows water to flow from the tap, but not back in. They can be purchased at any hardware store.

Also, you can use an air gap of at least one-inch or two times the pipe diameter (whichever is greater) between the end of a hose and the source of the contamination. This eliminates a link between the two. Never leave a hose where it can pull contaminants back into your home supply- such as a swimming pool, bathtub, sink, fish tank or garden sprayer.