San Mateo County Environmental Health Services manages Menlo Park Municipal Water’s Cross Connection Control program. This program protects the City’s drinking water system from contamination caused by backflow. The County’s services include notifications, record keeping, tester certification and site surveys for cross-connection compliance. 

A cross-connection is any connection between a safe drinking water system and any other untested water source, system, or equipment that may contain unsafe substances. When an undesirable condition known as backflow occurs, water can flow in the opposite direction and may bring contaminants or pollutants into the public drinking water supply through a cross-connection. A backflow prevention assembly is a mechanical device that prevents water from flowing backward.

Cross connection control through backflow prevention is required in a variety of applications. Irrigation water meters, multifamily housing, as well as all commercial and industrial properties are required to have backflow prevention assemblies. Single family residences generally do not have and are not required to have a backflow prevention assembly. We have 675 backflow prevention assemblies at the service connection (next to the meter), and 408 located onsite. 

Prevent backflow by ensuring your backflow prevention assembly is tested by a County-certified backflow prevention tester annually. The County mails notifications as a reminder to have your backflow prevention assembly tested each year. If you have a backflow prevention assembly that has never been tested, notify the County and Menlo Park Municipal Water immediately.

For additional information, please visit the San Mateo County Health’s Cross Connection Control Program webpage or contact Assistant Engineer Scott Jaw.