If you have a well on your residential OR commercial property (whether it is in use or not), you must ensure that it is in compliance with Redwood City’s Cross Connection Control Ordinance and California State Water Resources Control Board – Division of Drinking Water Title 17 Requirements.


The Cross Connection Control Ordinance is in place to protect the drinking water supply from contamination that might occur because of backflow, or the undesirable reverse flow of non-drinking water into a drinking water system.

cross-connection is a connection or potential connection between drinking water and any other system that may contain harmful substances that could possibly enter the drinking system. Cross connections happen whenever the plumbing system is connected to the drinking water supply. For example, this could happen in:

  • Swimming pools
  • Landscape irrigation
  • Ornamental ponds

Since cross-connection can happen at wells due to backflow. Two primary causes of backflow are backsiphonage, or lack of pressure (vacuum) and back pressure, or too much pressure.

To prevent this, the Cross Connection Control Ordinance was passed, requiring operational wells to have a backflow assembly or a device that prevents backflow. Additionally, ALL wells and backflow assemblies must be tested or inspected annually to ensure safety. Click here to see how to ensure your well is safe.