Cross Connection / Back Flow

What is cross connection?

A cross connection is defined as any actual or potential physical connection between a public water system or the consumer’s water system and any source of non-potable liquid, solid or gas that could contaminate the potable water supply by backflow.

Washington State Department of Health (WA 246-290-490) requires by law, that water systems shall protect the public water systems from contamination via cross connections.

Types of cross connections include, but are not limited to:

  • Irrigation systems
  • Fire sprinkler systems
  • Boiler heating systems
  • Swimming pools
  • Hot tubs
  • Ponds
  • Auxiliary Wells

Drinking water systems may become polluted or contaminated in the distribution system through uncontrolled cross connections. 

Washington State Department of Health and ALWA require all cross connections or backflow systems be tested annually by a state certified Backflow Assembly Tester (BAT). The tests are due by June 30th each year. ALWA has a list of testers that frequently service our area; however ALWA does not endorse any particular tester. Click here for the list of testers.

If your backflow system fails the test, repairs must be performed immediately. A backflow assembly that has failed will not protect our water supply. Once the system is repaired, another test must be completed and the passing report must be sent to our office.

For any questions please call us at 425-222-7003 or email at

Thank you!