San Mateo County Cross Control Program


San Mateo County Backflow Testing


Cross Connection Control Program


The Health System’s Environmental Health Services contracts with water purveyors to implement a cross-connection program as mandated by the State Resources Control Board, Drinking Water Division (formerly under the California Department of Public Health), Title 17 of the  California Code of Regulations, and the State Health and Safety Code.

The following water purveyors are a part of the San Mateo County Cross Connection Control Program as illustrated in this map:

The Cross Connection Control Program protects the public drinking water supply in San Mateo County. As a part of the San Mateo County Cross Connection Control Program, surveys and/or inspections are conducted at facilities or services that may pose a threat to public health and safety. To eliminate the cross connection or threat to public health, the installation of a backflow prevention assembly may be required in order to abate the public health hazard.

In addition to conducting inspections and certifying testers, Cross Connection Control Program staff work with large water suppliers in the following ways:

  • Ensure that the potable water supply is protected by the installation of backflow prevention assemblies and verify the annual maintenance/testing of these assemblies

  • Certify and audit Backflow Prevention Assembly Testers

  • Check plans

  • Consult with varying agencies and the public on how to prevent backflow

  • Train personnel

FAQs—General Information

1. What is a cross-connection?

A cross-connection refers to an unprotected actual or potential connection between a potable water system used to supply water for drinking purposes and any source or system containing unapproved water or a substance that is not, or cannot be, approved as safe, wholesome and potable.

2. What is backflow?

3. What is a backflow prevention assembly and what does it look like?

4. Why do I need a backflow prevention assembly or device?

5. Why I am receiving a notice to test a backflow prevention assembly?

6. Where is the backflow prevention assembly located on my property?

7. This is the first time I am receiving a backflow prevention assembly test notice, but I have been the property owner for more than a year.

8. I have received a cross connection control survey (or a link to an online survey) in the mail. Why did I receive this?

9. How should a backflow prevention assembly be installed?

10. Which water purveyors are part of the San Mateo County Cross Connection Control Program?

FAQs about Testing Backflow Prevention Assemblies (BPAs)

1. Why do I need to have my backflow prevention assembly tested?

2. How often is a backflow prevention assembly supposed to be tested and who can test backflow prevention assemblies?

3. What will happen if I don’t have my backflow prevention assembly tested?

4. What do I do if my backflow prevention assembly fails the annual field test?

5. What happens if I do not get my backflow assembly tested even after a third notice?

6. What is the due date by which I need to have my backflow prevention assembly tested?

7. I had my backflow prevention assembly tested already this year. Why am I still receiving test notices in the mail?

8. I have sold my property to another owner, but I am still receiving a test notice for a backflow prevention assembly. What should I do?

9. How do I change owner and/or mailing information on the test report form?

10. I am a backflow prevention tester, and I am interested in becoming a tester on your list.