Cross Connection Control & Backflow Prevention

What is a Cross-Connection?  

A cross-connection is an interconnection between drinking water from a public water system and a non-potable water source through any actual or potential connection. Examples of non-potable sources can be: commercial, industrial, fire systems, irrigation, recycled water, graywater, wells, swimming pools, and residential water services. 

What is Backflow? 

Backflow is the undesirable or unintended reversal of flow of water that may contain hazardous liquids, gases, pathogenic substances, or other undesirable qualities from a water customer’s internal water system back into our water distribution system/drinking water supply. 

The two primary hydraulic conditions that cause backflow to occur are

  • Back-Siphonage - A sudden decrease of pressure in the potable water distribution system that causes a vacuum, pulling non-potable water back into the system - Water Main Breaks, Fire Fighting, etc.
  • Back-Pressure - When the pressure in a customer's internal water system is higher than the potable water distribution system pressure, forcing non-potable water back into the water system – Elevation Differences, Pumps, Boilers, etc.

Properly installed and maintained backflow prevention assemblies are a form of Cross-Connection Control that provide protection against the threat posed by the many hazardous materials and/or conditions listed above. 

TO REPORT A BACKFLOW INCIDENT, UNPROTECTED CROSS-CONNECTION, LEAKING, DAMAGED OR STOLEN BACKFLOW PREVENTION ASSEMBLY, CONTACT THE CITY’S CROSS-CONNECTION SPECIALIST IMMEDIATELY: 

Annual Backflow Prevention Assembly Inspection & Testing 

Federal and State laws require that water utilities protect their public water system from pollution (non-health hazard) and/or contamination (health hazard) due to cross-connection backflow into the potable water distribution system. To preserve the integrity & safety of our public drinking water supply, the City of Milpitas enforces the state requirement that water customers complete an annual performance test of their backflow prevention assemblies installed on active water services, ensuring that they are functioning properly and providing protection against backflow as designed.  

As a courtesy, the City’s Utility Engineering Section sends a series of notices to customers/owners informing them of inspection & testing requirements each calendar year. If deficiencies are identified during the inspection portion or an assembly cannot produce passing test values, these issues must be corrected within 30 days, or it will result in the immediate termination of your water service. Our request follows the City's Ordinance, Number 232 of the Milpitas Municipal Code, Section VIII-3-3.01 which states:  

No water service connection to any premises shall be installed or maintained by the City unless the water supply is protected from contamination and pollution. Service of water to any premises shall be discontinued by the City if a backflow prevention device required by this Chapter is not installed, tested and maintained, or if it is found that a backflow prevention device has been removed, by-passed, or if any unprotected cross-connection exists on the premises. Service will not be restored until such conditions or defects are corrected. 

Note: An annual application packet & fee will be required from testers and must be approved by the Cross-Connection Specialist to be added to/remain on the list of approved backflow assembly testers each year. Backflow test reports will NOT be accepted by those who were denied from and/or are not on the list.  

For more information, visit our Qualified Testers & Cross-Connection Specialists page.

Hazard Assessments

In addition to the annual backflow prevention assembly inspections & testing, the water customer is responsible for completing a Hazard Assessment of their site(s) as required by the CA State Water Resources Control Board (SWRCB) Cross Connection Control Policy Handbook (CCCPH) Article 2, Section 3.2.1 where it states: “All water services that are connected to a public drinking water system are to complete an initial assessment of their site.” 

Visit the Hazard Assessments page for more information.