Mesa Water is committed to protecting the health of its customers by providing safe, reliable, high-quality water to the communities we serve. Here are just some of the methods we use to validate the safety and cleanliness of our water supply.

Backflow Prevention

Water distribution systems are carefully designed to ensure a smooth flow of water from the distribution system to the customers. While rare, certain hydraulic conditions can cause water to deviate from its "normal" flow and move in the opposite direction.

To safeguard the public water supply from potential sources of contamination and optimize water quality, Mesa Water implements a comprehensive cross-connection program. This program is specifically focused on identifying and eliminating potential cross-connections.

One of the most critical aspects of our cross-connection program is backflow prevention. Its primary objective is to prevent reverse flow into the water distribution system. This is achieved by installing reliable backflow prevention assembly devices at water meters to protect the integrity of the public water supply.

Cross-connections, whether permanent or temporary, can pose risks. At Mesa Water District, we take proactive measures and coordinate inspections to ensure that backflow prevention devices are installed correctly and in compliance with laws that protect the public water supply. We work with State, County, and other local agencies to assist our customers in following the proper procedures for installing and maintaining backflow prevention systems.

Compliance with these regulations is a crucial part of our commitment to water safety. The Safe Drinking Water Act Amendments of 1986, the California Code of Regulations, and Mesa Water’s Rules and Regulations all mandate that water users must have their backflow prevention devices tested annually. If necessary, any required repairs must be carried out by the customer, followed by a retest of the device. These annual tests must be performed by a backflow prevention device tester certified by the Orange County Health Care Agency and sent to Mesa Water District and the Orange County Health Care Agency.

Send Copies of Completed Test Reports to Both Agencies

Mesa Water District
Attn: Water Quality
1965 Placentia Avenue
Costa Mesa, CA 92627-3420

Orange County Health Care Agency
Cross Connection
1241 East Dyer Road
Suite 120
Santa Ana, CA 92705-5611

Backflow Documents

*PLEASE REPORT ANY BACKFLOW DEVICE THEFTS TO the water quality department 949-754-1031

Due to the potential of theft in commercial and industrial areas, installation of a backflow enclosure should be considered for the protection of your device.


The Mesa Water supply, like Metropolitan Water District, is treated with chloramines, a combination of chlorine and ammonia. Chloramines are effective in controlling the growth of bacteria and other microorganisms that may cause disease. Chloramines form fewer disinfection byproducts and may have no odor.

People who use kidney dialysis machines may want to take special precautions and consult their physician for the appropriate type of water treatment before consumption. Also, customers who use fish ponds, tanks or aquaria should also make necessary adjustments in water quality treatment, as the disinfectants may be toxic to fish.

Water Main & Hydrant Flushing

As part of Mesa Water's regular preventative maintenance program to remove normal sediment buildup from the pipes that deliver water to its customers, Mesa Water performs unidirectional flushing of the water mains and fire hydrants. This improves the quality and appearance of the water.

Customers will be notified when flushing is scheduled to begin in their area. During flushing you may notice some discoloration or sediment in your tap water, affecting only its appearance. The water is safe and will clear up in a few minutes when you run cold water through the faucet of your bathtub or other unscreened tap such as a backyard garden hose.

For more information on Mesa Water's flushing program call the Water Quality Department at 949.574.1031.