To protect the public water mains from potential contamination by non-potable "used water" that could be drawn in from the private customer side during a sudden pressure drop, the City requires installation of a backflow prevention device on new services. The device must be approved by the State Water Resources Control Board.
To see the current list of approved backflow prevention devices, stop by the Water Division office, or contact the State Board's Division of Drinking Water directly at 916-449-5577 to request a copy. To minimize the visual impact of these devices, consult City of Napa Backflow Screening Guidelines (PDF).
All installed devices must be tested annually by a certified backflow prevention tester and immediately repaired if necessary. Notice letters are sent to customers each year regarding this testing requirement.