Water normally flows in one direction, from the public water system through the customer’s cold or hot water plumbing to a sink tap or other plumbing fixture. The plumbing fixture is the end of the potable water system and the start of the waste disposal system.
Under certain conditions, water can flow in the reverse direction. This is known as backflow. Backflow occurs when back siphonage or backpressure condition is created in a water line.
Back siphonage is caused by negative pressure in the supply line to a facility or plumbing fixture. Backsiphonage may occur during waterline breaks, when repairs are made to the waterlines, and when shutting off the water supply.
Backpressure can occur when the potable water supply is connected to another system operated at high pressure or has the ability to create pressure. Principal causes are booster pumps, pressure vessels, and elevated plumbing.
To prevent these kinds of incidents, backflow preventer devices are required at services with known hazards. A backflow preventer is a mechanical device designed to prevent backflow through cross-connections.
City of Stanwood Approved Devices
- Double Check Valve Assembly (DCVA)
- Reduced Pressure Backflow Assembly (RPBA)
Test Your Backflow System Annually
Annual testing of your backflow system is required by Washington State Code (WAC) 246-290-490 (link is external) to assure that it is in perfect working order. The yearly test will identify any problems so they can be corrected.
Each address within the City of Stanwood that contains a backflow device is assigned an account number and a yearly due date for inspection of that device. Reminder letters are mailed each month for the devices that are due to be tested, along with detailed account information.
If an annual test is not performed, we will be required to terminate the water service at that particular address. Water service will only be restored when the backflow devices are in compliance with Washington State codes.
Failed Backflow Tests
If your backflow system fails the test, repairs must be performed immediately. A backflow assembly that has failed will not protect our water supply. The tester you have hired will be able to assist you with this issue. Your account cannot be considered current unless or until each backflow assembly has passed the tests.
Certified Backflow Assembly Testers
Any state-certified Backflow Assembly Tester (BAT) is able to perform this test. The City of Stanwood maintains a list of certified testers as a convenience to our customers. A copy of this list is included with the yearly mailing of your account information, test forms, and due date.
These testers have requested that their company names appear on our current list. This list does not include all certified BATs, and is not a recommendation to hire. If you wish to hire an individual whose name does not appear on this list, contact the Washington State Department of Health to confirm their certification.