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Water Services

Cross Connections Program

Metro Water Services’ Cross Connection Control Program protects our community’s drinking water supply by preventing backflow contamination.

Backflow can occur when a change in pressure in the water system causes water in the pipes to flow in the reverse direction. This change in pressure has the potential to pull contaminants into the drinking water distribution system.

A cross-connection can occur when non-drinking water is unintentionally able to mix with drinking water.

Our Cross Connection Control Program regulates and inspects both commercial and residential buildings for conditions that could put our community’s drinking water system at risk for contamination.

Your participation in the Cross Connection Control Plan is critical in helping MWS protect the public water system from cross contamination and ensure safe drinking water for all its customers. Thank you for your efforts.

Required Annual Inspections

In order to meet state requirements, every backflow device must be inspected by Metro Water Services or our contractor annually. We schedule inspections geographically.

  • Annual Inspection Cost
    • Each inspection costs $42* per device during normal business hours.
    • Additional charges will be applied for after-hour inspections.
    • Backflow inspection charges will appear on your water bill.
  • Failed inspections
    • If the backflow assembly fails inspection, we give the customer a timeline to address the issue.
    • The timeline will range from immediate disconnection to ninety days, depending on the level of hazard.
    • Re-test visits will continue until the customer has taken all corrective action to ensure backflow protection.
    • Customers will be charged $42* for each re-test.

*Price subject to change.

Commercial Backflow Requirements and Inspections

Metro Water Services inspects commercial locations and classifies them as either high hazard or low hazard.
Depending on the level of hazard, Metro Water Services may require

  • immediate protection,
  • immediate disconnection,
  • or customers may be given a certain amount of time to comply with regulations.

High-hazard commercial locations

  • Examples: restaurants, medical facilities, automotive industries, multi-story buildings, and multi-unit apartment complexes.
  • High-hazard locations require backflow prevention measures.
  • Metro Water Services will inspect and test the backflow device every twelve months.
  • For more examples of hazardous connections, see pages 9-10 of the Cross Connection Control Plan.

Low Hazard commercial locations

  • Examples: single-story buildings with no connection to an ice maker or any other device directly connected to a domestic water line. These locations could include a bank branch, an accounting office, a lawyers’ office.
  • Metro Water Services will visit commercial locations that do not require a backflow device a minimum of once every five years. During this visit, we will determine if any new conditions exist that require a backflow device.

Residential Backflow Requirements and Inspections

  • Potential cross connections concerns at homes include:
    • swimming pools,
    • hot tubs, and jacuzzis,
    • alternative water sources,
    • underground irrigation systems,
    • fire protection systems.
  • Any residence where a cross connection exists will be required to use proper backflow prevention measures. Metro Water Services will inspect and test the backflow device every twelve months.

Note: Buildings with three or more units (i.e. triplex or apartment complex) are considered commercial properties.

Installation of Backflow Devices

All devices must meet University of Southern California specifications.

Location of Backflow Devices

  • In general, backflow prevention devices should be placed directly behind the meter.
  • Any other location will require a variance approved by Metro Water Services Variance Committee. If you would like to request a variance, please see the Minimum Variance Requirements and Variance Request Form.
  • If your device must be placed inside a building and its location has been approved by the MWS Variance Committee, it must be placed in an area with:
    • 7 feet head clearance
    • Proper lighting
    • Easy accessibility
    • 3 feet clearance in front of device
    • All backflow devices must be placed in the same room, and the location of the room must be at a point of closest proximity to the meter.
  • If an existing backflow device requires replacement, it must be relocated to meet current Metro Water Services standards for installation and access requirements. This would apply to any "grandfathered" installation of a backflow device which had previously been inspected by MWS. Any remodeling project to the premises that adversely effects the access to the mainline backflow device would not be permitted and result in enforcement action for the customer connection.

Fire Service Installation Requirements

  • If more than twenty feet exists between the backflow prevention device and active water, an automatic flusher device must be installed to clear the water out of the water line periodically.
  • For a fire service, a backflow device can be put in vertically or horizontally.

Domestic Service Installation Requirements

For a domestic service (water lines connected to bathrooms, kitchens) a backflow device must be put in horizontally.

Additional Installation Information

Details and drawings for various backflow device requirements

More information regarding the approval of new installations can be found on pages 7 and 8 of the Cross Connection Control Plan.