Cross-Connection Control and Backflow Prevention Program
The District is committed to providing reliable, safe, and high quality drinking water to its customers. Part of that commitment involves the further development of a Cross-Connection and Backflow Prevention Plan. A Cross-Connection Control and Backflow Prevention Plan protects our drinking water by preventing contaminants from entering our water distribution system.
Is this a new program?
No! The plan became necessary when the federal government passed the Safe Drinking Water Act in 1974. Since then, a version of this plan has been in place at all public water systems in California, under the California Department of Health, Title 17 in the California Code of Regulations. The State made the most significant changes to the program requirements in adopting the Cross-Connection Control Policy Handbook, effective July 1, 2024.
So what is a cross-connection?
Cross-connections are actual or potential connections between a potable water supply and a non-potable water source.
What’s a backflow?
Backflow is the unintended reversal of water flow through a cross-connection, which can result in a potentially serious public health hazard. Backflow of untreated water through an unprotected cross-connection can lead to serious chemical or microbiological contamination in our water distribution system.
How does backflow happen?
A backflow condition can happen in one of two ways:
- Back-pressure. This happens when the water supply on a property is connected to a device that creates pressure greater than the pressure in the public water system, causing water to flow or push into our distribution system.
- Back-siphonage. This happens when there is a loss of pressure in our distribution system, causing water to be pulled into the system from an actual or potential cross-connection.
An actual cross-connection is one that is subject to both back-pressure AND back-siphonage.
A potential cross-connection is one that is subject to back-siphonage only.
What types of backflow preventers are there?
Air Gap
An air gap device provides a physical separation between the discharge end of a potable water supply line and an open or non-pressure receiving vessel. It’s the simplest type of backflow preventer, but is not appropriate for all situations.
Double Check Valve Assembly
A double check valve assembly (DC) is designed to allow water to flow in one direction only, and is composed of two independently acting, approved check valves, including tightly closing resilient seated shutoff valves attached at each end of the assembly and fitted with properly located resilient seated test cocks.
Reduced Pressure Principle Assembly
A reduced pressure principle assembly (RP) is composed of two independently acting approved check valves together with a hydraulically operating, mechanically independent pressure differential relief valve located between the check valves and at the same time below the first check valve. It also includes tightly closing resilient seated shutoff valves attached at each end of the assembly and fitted with properly located resilient seated test cocks.
Will I be required to install a backflow prevention assembly?
The District, in conjunction with the County of San Luis Obispo Environmental Health Services division, will work to identify any actual or potential cross-connections on each customer’s property. To prevent any backflow incidents, you may be required to install a backflow prevention assembly. A backflow prevention assembly is a testable device that uses check valves to prevent contaminated water from flowing backwards into the water distribution system.
If you are required to install a backflow prevention assembly, you will be notified by the District, and provided with additional information regarding what type of assembly to install and where it needs to be installed.
Additional Resources
County of San Luis Obispo, Environmental Health Services Cross-Connection Control Program
State Water Resources Control Board Cross-Connection Control Policy Handbook
USC Foundation for Cross-Connection Control and Hydraulic Research List of Approved Backflow Prevention Assemblies
