25122 Regal Drive

Abingdon, VA 24211



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Cross-Connection and Backflow Prevention Program

Modern Water Treatment Plants do a terrific job of cleaning and disinfecting raw water sources. However, recent case studies concerning water contamination have revealed that contaminants find their way into the water supply via the distribution system, not at the treatment facility.

A Cross Connection is any temporary or permanent connection between a potable (i.e., drinking) water system and any source or system containing non-potable water or other fluid. These occurrences can be as obvious as an unprotected potable water line entering a wastewater treatment plant or as innocent looking as a garden hose left immersed in a bucket of cleaning solution.

Under normal operating pressures, these cross-connections may not present a threat to the drinking water supply. The problem occurs when pressure is lower on the potable or public supply side than it is on the non-potable side. Contaminants can reverse flow by back siphonage or back pressure.

Back Siphonage can occur when county water line pressure is greatly reduced by a line break or under conditions of high usages, such as a fire flow. Non-potable substances can be drawn to the water main through any existing cross-connection. For example, if a 6-inch water main develops a leak, WCSA crews have to cut off water service on that particular line to make repairs. As the remaining water in the line flows out of the leak, water in unprotected homes and businesses reverses flow. At this point, something toxic could enter the public water system.

Back Pressure can occur when pressure on the customer’s side overcomes normal operating pressure on WCSA’s side. For example, the use of boilers and water pumps could create a situation where customer-side pressure forces contaminants back into the public water system. New WCSA customers that previously had a well or spring with associated pumps and pressure tanks could be a source of backflow due to back pressure. WCSA customers served by new line extensions must provide proof of physical disconnection between their old private water systems and the WCSA system.

If necessary, a WCSA representative can inspect the customer’s system before service is established.

Remember, by taking measures to prevent backflow, you are protecting members of your own household.

To download our Cross Connection and Backflow Prevention Program, click here.

If you have additional questions about cross-connections or backflow, please call WCSA or visit the following websites:

USC Foundation for Cross-Connection Control and Hydraulic Research
American Backflow Prevention Association
Watts Backflow Prevention