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Backflow Prevention


Backflow Prevention Assembly Testing Report Form
Certified Backflow Prevention Assembly Testers (Partial List)
Water Service Area
Cross Connection Control Program


At the 1933 Chicago World’s Fair, 98 people died from Dysentery due to sewage from the toilets that backed up into the water system. More recently, the neighbors to a food processing company discovered that their water was tainted with apple juice; not a health hazard to most but the coffee probably tasted funny. These events and many others like them are the result of cross connections. A cross connection is any potential or actual physical connection between potable water and a non potable fluid. These connections can range in severity from severe hazards (involving sewage or hazardous substances) to aesthetic problems (juice, dirt, etc.).

Examples of potential cross connections include automatic lawn sprinkler systems, fire sprinkler systems, carbonated beverage machines, carwashes, and dry cleaners. Even in your own home, you can unwittingly create a cross connection by putting the garden hose in a swimming pool, pet’s water bucket or fish tank to fill it or putting it down the drain to flush out debris when it’s backed up or connecting your garden hose to a plant fertilizer or bug spray unit.

Without protective devices and assemblies (referred to as backflow prevention assemblies), the potable water supply can become contaminated by any customer in the system. A Cross Connection Control Program is required by the Washington State Department of Health and the United States Environmental Protection Agency (through the Safe Drinking Water Act) to protect the public from contaminated water. This program calls for facility inspections to identify and eliminate cross connections as well as annual testing of backflow prevention assemblies.

Although many people are not aware of it, we see a common backflow preventer every day. The average household sink, whether in the bathroom or a kitchen, utilizes an air gap to prevent the potable water supply from becoming contaminated. Other appliances that utilize water (namely, clothes washers) have built-in backflow preventers as well. Some businesses, specifically hospitals and shops that use hazardous chemicals, are isolated from the rest of the system with heavy duty backflow prevention assemblies.

It is the City’s responsibility to protect customers from contaminated water; Kirkland’s Water and Building departments work together to provide this protection. The Public Works Department manages the Cross Connection Control Program and tracks the results of annual backflow prevention assembly testing (conducted by certified Backflow Assembly Testers). The Building Department performs inspections of new construction to determine what cross connection precautions are required, if any. Customers are encouraged to assist with the success of this program by attaining the proper permits for plumbing changes (including new irrigation installation) and arranging for annual testing of existing assemblies by a certified tester.

Any questions regarding this program can be addressed by Van Sheth, in the Public Works Department at 425-587-3907.

If you rely on an irrigation system for watering your lawn and plants, here are some tips on keeping your landscape healthy while making every drop of water count.

To print the Backflow Prevention Assembly Testing Report Form and to view the printable format of the Certified Backflow Prevention Assembly Testers Partial List, you will need Adobe Acrobat Reader (a free program).  Get Adobe Acrobat Reader.


Public Works
123 5th Avenue, Kirkland WA 98033
T. 425-587-3800 | F. 425-587-3807
Mon-Fri, 8 a.m. to 5 p.m.

Operations & Maintenance
915 8th St, Kirkland WA 98033
T. 425-587-3900 24/7 | F. 425-587-3902
Mon-Fri, 6:30 a.m.-3:30 p.m.

General Inquiries - Contact us via the: 
Our Kirkland Customer Service Portal