What is backflow prevention, and how does it protect my water supply?

Backflow prevention is the act of using a mechanism or device designed to stop the backward flow of water or other substances into the primary water supply. Its purpose is to safeguard water quality and safety by preventing contamination from entering the water system. Most people associate backflow prevention with being connected to a public water supply. However, it is just as important for private well owners to ensure their systems stay safe from backflow.

Backflow can occur due to various reasons, including changes in water pressure, a broken pipe, a cross-connection with your septic tank, or the use of certain equipment that can create a siphoning effect. Figure 1 shows you how backflow can occur in a private well system. Seemingly innocent acts such as filling a pesticide or fertilizer canister with water can put your well at risk. Well owners should be aware of these potential sources and take necessary precautions to prevent backflow.

Backflow prevention devices are typically installed at the point where the water supply connects to a plumbing system or a specific water outlet and ensures that water flows in a single direction. There are different types of backflow prevention devices that are suitable for use with wells. One option is an anti-backflow device, such as a check valve, which prevents unwanted reverse flow of liquids back down a water supply pipe into a well. Another option is an air gap device, which creates an open space between the hose or faucet and the liquid level, preventing backflow of liquids into the well or water supply.

If you do not have a backflow prevention device or have questions about an existing device, consult with a licensed plumber or your local health department for specific guidance based on your individual well system and local regulations.