About Cross Connection and Backflow Prevention Devices

In order to protect water quality and prevent the spread of infectious disease and other contaminants, we must protect clean water from accidentally being contaminated by dirty water when pressure drops in a water system. Each point where clean and dirty water come together is called a cross connection and must be carefully built and controlled.

When cross connections are not properly maintained or designed, the dirty water can mix into the clean water supply. That is called backflow. Backflow can occur because of sudden changes to pressure that may sometimes happen. It can be necessary to install a backflow prevention device to keep backflow from happening. In Los Angeles County, the devices must be tested every year by one of our Certified Backflow Tester.

Find a Certified Backflow Tester

If you want to become one of our certified backflow device tester in Los Angeles County, please visit our Certified Backflow Testers page.

The Cross Connections and Water Pollution Control Program is responsible for inspecting industrial, commercial, and medical facilities to ensure that no hazardous conditions exist between plant equipment, process waters, plumbing fixtures and the potable water system. If a hazard is found, we require the consumer to install an approved backflow prevention device. The device must be tested every year by a certified tester. This program also certifies over 700 backflow prevention device testers and keeps a database of over 51,000 backflow prevention devices. Listings of the Approved Devices are available in the documents section, below. This program also provides technical assistance to many County and State agencies, local water utility companies and building inspection agencies.

The Cross Connection and Water Pollution Control Program identifies cross connections through the inspection and evaluation of a consumer’s water supply to determine whether solid, liquid or gaseous pollutants or contaminants are allowed to enter the potable water system.

  • When a hazard to the potable water system is found, the consumer is required to install an Approved Backflow Prevention Assembly at a key location within the system to circumvent the contamination.
  • The type and location of the backflow prevention device is dependent upon the nature of the hazard and complexity of the onsite piping.
  • The backflow prevention assembly is approved based upon specifications developed jointly by regulatory agencies, plumbing official and the manufacturing industry. The laboratory work of the Foundation for Cross Connection Control at the University of Southern California and the Mechanical Testing Laboratory of the City of Los Angeles, Department of Building and Safety are essential elements of this program.
  • The laboratory and field approval process of the following groups are essential in developing a reliable listing of approved backflow prevention devices: Foundation for Cross Connection Control and Hydraulic Research at the University of Southern California; and the Mechanical Testing Laboratory of the City of Los Angeles Department of Building and Safety.
  • Since all mechanical devices are subject to failure, the on-going program for the Certification and Re-certification of the Device Testers, as well as the database of backflow prevention device test results are critical in maintaining the integrity of these devices.

A listing of currently approved backflow prevention devices, both testable and non-testable is maintained to provide the public with the most reliable hardware available.

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