Backflow assemblies are devices installed on water service lines or at plumbing fixtures that prohibit the backflow of water. Two types of backflow prevention devices are commonly used to contain contaminants within service connections - the double check valve assembly (DCVA) and the reduced pressure backflow assembly (RPBA). Both types use check valves to prevent water from flowing backwards through the pipes.
The DCVA is utilized to prevent a cross-connection when the backflow would not be hazardous to one's health. The DCVA consists of a shut-off valve on either end and two check valves in the center. When water flows in the normal direction, the check valves are forced open by the flow of water.
The RPBA is more complex, adding a hydraulic spring-loaded pressure differential relief valve between the two check valves. This addition makes the RPBA suitable for cross-connection control where the backflow could create a danger to public health.
Washington State law requires backflow assemblies to be field tested after installation and annually thereafter to make sure the device is working properly. The District sends out notices to remind of upcoming reporting in advance of due dates. Two documents, a form
Backflow Prevention Assembly Test Report (PDF) and document
Backflow Assembly Tester Resource List are provided in that notice. Should you have further questions or need additional information, please
Email Chris Zoepfl, Cross-Connection Control Program Manager or call (253) 946-5427.