Backflow prevention device testing

Question: The city recently sent me a notice to have my backflow assembly tested. What is that, and why is the city asking me to have it tested?

Answer: Our public water system is threatened by contamination from several sources. We are responsible for and need to maintain our backflow prevention assembly. The city sends out reminders and information in March and April each year.

Many of our homes have a backflow prevention assembly, a device intended to prevent water from re-entering our drinking water pipes and contaminating our water supply. Common cross-connections that create this potential problem include irrigation systems, pool equipment, fire sprinkler systems, dock water supply, boilers and radiant floor heating systems. Other common residential systems that may have these devices include water features and boat lifts.

When water is connected to an irrigation system and there is a large demand placed on our water system, a vacuum can be formed. Water can back-siphon or flow back into our drinking water pipes. Think of water already in your yard, irrigation pipes and several appliances creating demand simultaneously; we can draw water that is contaminated back into our drinking water. Other causes can be a fire hydrant in use, a water line break, or maintenance work causing a drop in pressure, which can lead to very undesirable results.

We frequently find that older irrigation systems, many designed and installed by homeowners, are missing these devices. If you have an irrigation system, protect your family and have the system inspected and tested. In my case, a boiler connection could allow water that has been piped through my floors and heating system for years to be mixed with my drinking water. Potential contaminates include bacteria, fertilizers, pool and lake water.

These systems are mandated by the State Health Department, building codes and the city’s water department. Irrigation systems, fire sprinkler systems, pools and boilers all require backflow assemblies. They require installation and annual testing of these valves — which do fail — by state-certified testers. Your city notice includes a listing of testers, and it typically costs between $40 and $60 per device.

Protect your families and the Island's water supply and have your device tested. Be sure to ask your tester if you might have other cross-connections, to be safe. If, like me, you discover that you have or might have an assembly, contact Sandy Love at the city of Mercer Island for more information and help with identification. The city sends out reminders to all of the homeowners who are on record, but many are not listed and may cause problems for us all. The city has current records of 3,247 sites; please check yours to keep us all healthy. Sandy can be reached at (206) 275-7782.

Steve Bryan owns Home & Building Services, Inc. and is an Island resident. He can be reached at or 232-2473.

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