Backflow testing companies in Washington

The lists we use in Washington

• City of Bellevue backflow testing companies, City of Bellevue Utilities: 201 companies based in Washington, as of February 19, 2025.
• Washington Water companies with certified backflow testers, Washington Water Service: 70 companies based in Washington, as of January 14, 2026.
• City of Spokane backflow assembly testers, City of Spokane Water Department: 54 companies based in Washington, as of February 4, 2026.
• City of Olympia certified backflow testers, City of Olympia Drinking Water Utility: 35 companies based in Washington, as of July 28, 2026.
• Clark Public Utilities list of Washington State certified backflow testers, Clark Public Utilities: 26 companies based in Washington, as of March 2, 2026.
• City of Lacey certified backflow assembly testers (BAT) list, City of Lacey Public Works: 23 companies based in Washington, as of April 30, 2025.
• City of Yakima certified backflow prevention assembly testers, City of Yakima Water/Irrigation Division: 22 companies based in Washington, as of October 7, 2026.
• City of Ridgefield approved backflow assembly testers, City of Ridgefield Public Works: 19 companies based in Washington, as of April 30, 2026.
• City of Sumner approved backflow assembly testers, City of Sumner: 17 companies based in Washington, as of January 5, 2026.
• City of DuPont certified backflow prevention assembly testers, City of DuPont Public Works: 14 companies based in Washington, as of March 17, 2026.
• City of Snoqualmie backflow assembly testers, City of Snoqualmie: 10 companies based in Washington, as of July 23, 2025.

Being on a utility's list means that utility lets the company file backflow test reports in its system. It is not a state license. See Washington backflow rules and how testers are certified.

Backflow testing businesses in Washington

Ranked by our quality score: on the utility's current list, a phone that matches the business's Google profile, and a website. Nobody can pay to move up.

Towns with approved testing companies

• Auburn
• Bellevue
• Burien
• Gig Harbor
• Issaquah
• Kent
• Olympia
• Pacific
• Poulsbo
• Puyallup
• Redmond
• Renton
• Richland
• Seattle
• Spokane
• Spokane Valley
• Tacoma
• Tukwila
• Tumwater
• Vancouver
• Woodinville
• Yakima

All 102 backflow testing businesses in Washington, by town

Every listed backflow testing company, A to Z

Water utility backflow programs in Washington

Your utility sets your deadline, the testers it accepts and how the report is filed. Each page quotes the utility's own rules.

• Seattle Public Utilities
• Tacoma Water

Questions