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Help Us Keep Your Water Safe with Cross Connection Control

Keeping water safe is a two-way street. We rely on you, our customers, to be aware of any cross connection to the water system that you might have on your property, and to protect those connections with a Backflow Prevention Device to ensure the safety of our drinking water.

What is a Cross Connection?


A cross connection is a point in a plumbing system where it is possible for a non-potable substance to come into contact with the potable drinking water supply.


For homeowners, these commonly include irrigation systems, private fire sprinkler systems, boiler systems, and pool or pond equipment.

What is Backflow?

Backflow occurs when water or other substances flow in the opposite direction than intended—such as the water in an irrigation system flowing back towards the water source once it's turned off—which allows contaminants to enter the public water system or consumer's plumbing.


A backflow incident occurs when biological, chemical, or physical contaminants enter the drinking water supply (under backflow conditions) via unprotected cross-connections. Backflow incidents may cause injury, illness, or death.

What is Required to Keep Water Safe?

In our complex water system, everything is connected. Washington State Administrative Code (WAC 246-290-490) requires customers to install, maintain, and test Backflow Prevention assemblies (examples shown above) to keep pollutants and contaminants from entering the clean drinking water system and prevent backflow incidents.


This same Code requires Silver Lake Water & Sewer District maintain a backflow prevention program, in which we send out annual reminder letters to customers with Backflow Prevention Devices when their device's annual test is due.

What Are Your Responsibilities?


If you have irrigation, fire sprinkler or other water-using systems, you will need to:

  1. Have a Backflow Prevention Device installed at the connection between your systems and the District's public water system;

  2. Have a state certified Backflow Assembly Test performed annually (see a link to a list of certified testers below); and

  3. The tester is required to send in your test report using our online portal: Tokay WebTest Portal.

Additional District Resources
Outside Resources
If you are an existing backflow customer, be sure your information is up to date for receiving reminders, and get your annual test scheduled in advance.  If you have questions about your due date, or need a list of registered testers, or have any questions at all, please contact us:
(425) 659-2304
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