A cross-connection is any point where a customer’s plumbing could let water, chemicals, or other substances flow backward (“backflow”) into the public water system. Backflow can happen when pressure in the water main drops, for example during a main break or firefighting, and pulls water back out of a building, or when a pump, boiler, or irrigation system pushes water back into the main.

Why it matters

Every home and business in Chester shares the same water system. One unprotected connection, such as a garden hose in a chemical sprayer, an irrigation system, or a boiler, could contaminate water for the whole community. A backflow prevention device is a one-way valve that stops that from happening.

Who requires it

The State Water Resources Control Board’s Cross-Connection Control Policy Handbook, which took effect July 1, 2024, requires every public water system in California to run a cross-connection control program. The District’s Board of Directors adopted Chester’s program by ordinance on May 12, 2025.

Our part: what the District does

• Surveys homes and businesses that may pose a backflow hazard, such as properties with fire sprinkler systems that use antifreeze, irrigation or recycled water, medical and dental offices, car washes, RV parks, and gas stations.
• Notifies the owner in writing if a device is required, with the type of device needed and lists of approved devices and certified testers.
• Keeps the test records for every device in the system.
• Protects the public water system if a hazard is not corrected.

Your part: what property owners do

• Install the device. If the District says your property needs a backflow prevention device, the owner pays to buy and install it.
• Test it every year. Each device must be tested at least once a year, and after it is installed, moved, or repaired, by a certified tester. Send the results to the District.
• Keep it working. Repair or replace a device that fails its test.
• Tell us before you add a hazard. Call the District before installing irrigation, a fire sprinkler system, a boiler, a pool, or a private well connection.
• Use a hose vacuum breaker. Never leave a garden hose sitting in a bucket, pool, or chemical sprayer without one.

If a required device is not installed, tested, or repaired after a series of written notices, water service can be shut off to protect everyone else’s drinking water.

Full ordinance: Cross-Connection Control Program Ordinance (2025) (PDF)

Questions about backflow testing or whether your property needs a device? Call the District office at (530) 258-2171.