Understanding Cross-Connection Control and Backflow Prevention

What is a Cross-Connection?

A cross-connection happens when the public drinking water system is directly connected to a non-potable source. This connection can allow water that is contaminated or unsafe to flow back into the clean water system, risking your drinkin water quality. Contaminants that can enter through the cross-connections include pesticides, fertilizers, bacteria, chemicals, and other pollutants.

Cross connections can be found in both homes and businesses. Common examples include:

• outdoor faucets
• toilets
• swimming pool fill lines
• heating systems
• irrigation systems
• fire sprinklers
• private wells

Managing cross-connections helps ensure your drinking water remains free from contamination.

What is Backflow?

Backflow happens when water flows in the opposite direction from its normal path, moving contaminants from a non-potable water source back into the clean water system. This reverse flow can occur due to changes in water pressure caused by heavy water use, water main breaks, or pumps in private plumbing systems.

There are two main types of backflows:

Why Backflow Prevention Matters?

Protecting the water supply from contamination is essential for public health and safety. Backflow prevention devices act as a barrier, stopping potentially hazardous substances from entering drinking water systems.

This protection is especially important in places where water is used for irrigation, heating, or industrial processes. These areas may involve chemicals or pollutants that should never reach the tap.

Maintaining effective backflow prevention helps ensure reliable access to clean water for everyone in the Tri-Valley and preserves trust in the water system.

How Backflow Prevention Works?

Backflow prevention relies on specialized devices installed in plumbing systems to stop water from flowing backward into the clean water supply. These devices use valves and air gaps to create physical barriers that block contaminated water from mixing with drinking water.

Common backflow prevention devices include vacuum breakers, double check valves, and reduced pressure assemblies. Each device is designed for different levels of risk and applications, from simple garden hoses to complex commercial systems. 

Who Needs Backflow Prevention Devices?

These devices are required for any property where water systems connect to equipment or processes that could introduce contaminants. This includes residential homes, commercial businesses, industrial facilities, and restaurants. 

As a property owner or business operator, it is your responsibility to ensure that backflow prevention devices are properly installed and maintained on your premises. If your property includes a cross-connection, such as an irrigation or fire sprinkler system, having a functioning backflow prevention device is essential. 

Responsibilities and Compliance

Zone 7 mainly supplies water to four retail community water systems: the City of Livermore, the City of Pleasanton, California Water Service – Livermore, and the Dublin San Ramon Services District. Additionally, Zone 7 serves one non-transient, non-community water system, which is the Lawrence Livermore National Laboratory.   These water systems are responsible for their own cross-connection control programs.

Zone 7 also provides water to a few direct customers through 12 service connections servicing its own Parkside field office, a residence, the Livermore Area Regional Park District, the Veteran’s Administration (VA) Medical Center, the Wente Winery, the East Bay Regional Park District’s Camp Arroyo, and a Department of Water Resources’ field sampling station.

Cross-connection control is a collaborative effort between Zone 7 Water Agency and our customers. By installing the appropriate backflow prevention devices and complying with testing requirements, you help safeguard our community’s water supply. Your attention to these safety measures prevents contamination and ensures that we can continue to deliver high-quality, safe drinking water to you and your neighbors.