Backflow & Cross Connection

Water normally flows in one direction, from the public water system through your water service, to your plumbing fixtures. However, under certain conditions water can flow in the reverse direction – creating “backflow”. Backflow can contaminate the water supply and cause serious health issues. Backflow is the reverse flow of non-potable water or other substances through a cross-connection hazard into the piping of the consumer's potable water system or the public water system.

A backflow prevention assembly is a mechanical device that prevents water from "backflowing" into a potable water system (either the consumer’s internal system, the public water system, or both).

The District can tell you which type of assembly is appropriate for your particular need. You may then choose the specific model from a list of approved assemblies available at the District office, or you can work with a Backflow Prevention Assembly General Tester or Cross-Connection Control Specialist to select a specific assembly.

In order to protect your family’s health and the public drinking water system, the State of California requires all water suppliers to maintain ongoing backflow prevention and cross-connection control programs so that your water is protected from hazards that originate on private property. The California Department of Public Health requires the District to eliminate cross-connections by maintaining these programs. The backflow prevention and cross-connection control program mandates the installation of backflow prevention assemblies by the consumer where the District determines they are needed, in accordance with Title 17 of California state law and District Water Ordinance 11.

The installation of the assembly must be inspected and approved by the District. Call the Water Quality Technician to schedule an inspection.

After the installation has been inspected and approved, the assembly must be tested. Per California State Law, all backflow prevention assemblies must be tested upon installation. A District-approved, certified Backflow Prevention Assembly General Tester must test the assembly to ensure that it is operating correctly and will complete the District’s “Backflow Prevention Assembly Test Report”, available on our website or at our office. The tester will then mail, fax, or email the completed form back to the District.

An auxiliary water supply is a water source on your property in addition to the public drinking water service. An auxiliary water supply can be any one of the following: well, lake intake, stream/river intake, spring, rainwater cistern, gray water, etc.

When there is an auxiliary water supply on a property, it can be a potential cross-connection if that auxiliary supply accidentally gets connected to the public drinking water supply. For example, if your property has a lake intake or a private well that feeds your irrigation system, but your irrigation system is also fed from the public water system, the water from the auxiliary supply could get into the public drinking water system. For properties with an auxiliary water supply, the District requires an approved backflow prevention assembly to be installed at the meter.

Yes. In our cold climate, fire sprinkler systems are typically charged with a glycol solution. Additionally, systems constructed out of black iron pipe typically contain a rust inhibitor. Even systems that are charged only with water may be hazardous to the water supply. Bacterial growth can occur in the stagnant water, which sits undisturbed in the pipes for many years. A loss of system pressure can draw this polluted or contaminated water into your own system and potentially into the District’s water supply. Systems that are charged only with air, but include a Fire Department Connection (FDC) also pose a hazard to the water supply; if the FDC is connected to a fire truck during a fire situation, the potential exists for water that may contain other substances to backflow into the drinking water supply.

Not for most hazards. However, when there is an auxiliary water supply, medical facility, lethal hazard,failure to allow the District to perform a cross-connection inspection, or other circumstance, as determined by the District, backflow prevention assemblies must be installed immediately behind the meter, on private property. RP backflow prevention assemblies installed at the meter must be installed in an above-ground, continually heated enclosure. DC backflow prevention assemblies installed at the meter may be installed in an underground box or vault, but must be approved on a case-by-case basis.

In general, the District has taken the approach of requiring internal protection with regards to the installation of backflow prevention assemblies, in order to protect the drinking water within the property as well as the public water system. This approach has been determined to be the best method for the protection of public health and safety. Furthermore, requiring internal protection, at the point of potential cross-connection, typically allows our customers to install smaller backflow prevention assemblies within their structure, and generally eliminates the need to house these assemblies in an above-ground, continually heated enclosure.

Failure to install the required type of assembly could result in termination of water service as described in the District’s Water Ordinance 11. The District will work with you to ensure that you are able to install the assembly, by selecting a location that would allow for the smallest size and fewest amount of assemblies, if more than one assembly is required. The District will also work with you to select a due date that is reasonable given your budget and schedule, while still addressing this matter in a timely fashion.

Yes! Backflow prevention assemblies, particularly irrigation assemblies, will freeze if left exposed. They must be kept from freezing by providing insulation and by providing a heat source, if needed. Irrigation assemblies are recommended to be installed with unions on either side, which will allow them to be removed during the winter months. Other assemblies can often be installed within the building in a heated area. District staff will help determine what location is appropriate for the assembly. We will endeavor to allow you to install the assembly within the building to prevent it from freezing.

Yes. The District owns and maintains 28 backflow prevention assemblies throughout our service area. We test all irrigation assemblies prior to first use each season, and test the remaining assemblies by the same due date as our customers.