• Cross-Connection Control


Sunnyvale Water Distribution
Cross-Connection Program

221 Commercial Street
P.O. Box 3707
Sunnyvale, CA 94088-3707

Phone - (669) 600-7322
Fax - (408) 730-7697

Cross-Connection Control

Am I In Compliance?

We will help determine whether your residence or business is in compliance with the cross-connection/backflow prevention regulations. Simply fill out the Cross-Connection and Backflow Protection Survey Form and either mail, fax or email it back to us. If you need a backflow device we will let you know within 30 days through Utility Billing.

Taking Measures to Protect our Water Supply

State regulations require that residential, commercial and industrial customers served by a public water system take adequate measures to protect the public water system from potential contamination. Under certain conditions, water from private plumbing can flow into the public water distribution system. This is referred to as backflow. The City is in the process of conducting site surveys to ensure that risks of backflow are mitigated. In order to prevent potential backflow, some customers will be required to install and maintain backflow prevention devices on the main water service lines.

What is Cross-Connection?

Cross-Connection is any actual or physical connection between a potable (drinkable) water supply and any source of non-potable liquid, solid or gas that could contaminate drinking water under certain circumstances.

What is Backflow?

Backflow is the reverse flow of water or other substances in to the treated drinking water distribution system. There are two types of backflow: backpressure and backsiphonage.

Backpressure happens when the pressure of the contaminant source exceeds the positive pressure in the water distribution main. An example would be when a drinking water supply main has a connection to a hot water boiler system that is not protected by an approved and functioning backflow preventer. If pressure in the boiler system increases to where it exceeds the pressure in the water distribution system, backflow from the boiler to the drinking water supply system may occur.

Backsiphonage is caused by a negative pressure (vacuum or partial vacuum) in the water distribution system. This situation is similar in effect to the sipping of water through a straw. In the drinking water distribution system, negative pressure (backsiphonage) occurs during a water main break or when a hydrant is used for firefighting.

Why Should You Be Concerned?

Backflow may affect the quality of the drinking water at your home, business or facility and has the potential to create health hazards if contaminated water enters your water supply plumbing system and is used for drinking, cooking or bathing. Backflow events occur more often than you might think although most do not create health hazards. Unprotected cross-connections with water supply plumbing or public drinking water piping systems are prohibited. We are all responsible for protecting our water supply from backflow that may contaminate our drinking water. It includes complying with the plumbing code and avoiding unprotected cross-connections.

Who is Responsible?

The responsibility for preventing backflow is shared. In general, state and local plumbing inspectors have authority over plumbing systems within buildings while state regulatory agencies and public water suppliers regulate protection of the distribution system at each service connection. Water customers have the ultimate responsibility for properly maintaining their plumbing systems. It is the water customer's responsibility to ensure that unprotected cross-connections are not created and that any required backflow prevention devices are tested in accordance with state requirements and maintained in an operable condition.

Preventing Backflow Situations In Your Home and Business

  • Be aware of cross-connections, eliminate or isolate them.
  • Maintain air gaps on sinks and when using hoses.
  • Do not submerge hoses or place them where they could become submerged.
  • Use hose bib vacuum breakers on fixtures (hose connections in the basement, laundry room, and on outside faucets/spigots).
  • Install approved backflow prevention devices on lawn irrigation systems and on fire sprinkler system services. Type of required backflow prevention devices will be determined based on the potential type of pollutants or contaminants; high, low or moderate.

Failure to comply can result in water service disconnection after repeated request from the Sunnyvale Water Program.

Private Wells

Backflow can also occur in the absence of a water main pressure drop. For example, some homes have backup water systems supplied by private wells or springs. If these systems are connected and overcome the pressure in the public water supply, backflow will occur. Because these private supplies are not tested and regulated by governmental agencies, they may pose a hazard to the potable water system and must be equipped with proper backflow prevention devices.


For additional information about backflow prevention, see the links below.

Backflow Assembly Testers

For information about cross-connection control requirements in Sunnyvale and forms for testing or installing devices, see the links below.


For More Information


City of Sunnyvale

Normal City Hours of Operation are
8 a.m. until 5 p.m.

(408) 730-7500

  • Sunnyvale City Hall
  • 456 W. Olive Ave.
  • Sunnyvale, CA 94086
  • TDD (408) 730-7501
  • Map and Directions 
  • City of Sunnyvale Logo

City of Sunnyvale

  • Sunnyvale City Hall

  • 456 W. Olive Ave.
  • Sunnyvale, CA 94086
  • TDD (408) 730-7501
  • Map and Directions

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