Cross connection contamination of the public water supply is the leading cause of waterborne disease in public water systems. Backflow prevention assemblies are devices that are installed in your water system to prevent water from flowing back into the public water supply.
The City of West Linn is mandated by the state to eliminate or control all cross connections. Annual tests of backflow devices must be performed by an Oregon State Certified Tester. Link to Oregon State Certified Backflow Testers 
For residential landscaping systems, tests must be done annually when the sprinkler system is activated, which is normally in the spring. Regardless, all systems must be tested no later than July 1st of each year.
Typically in May, individual postcards are sent to all backflow customers who, according to our records, have not had their assemblies tested. This is to officially notify these homeowners and business owners to have their backflow device(s) tested to avoid having their water shut off.
If you have questions about testing your device, call our Environmental Technician at our Public Works office at 503-656-6081.
For a list of certified testers click on the link included in the second paragraph of this page.