Backflow Prevention and Cross-Connection Control FAQs
Environment – Water & Sewer Utilities – Drinking Water – Backflow Prevention and Cross-Connection Control
What is a backflow?
Backflow may occur when downstream pressure becomes greater than the upstream (supply) pressure in a public or consumer’s potable water system. Backpressure may result from an increase in downstream pressure, a reduction in public water supply pressure, or a combination of both.
What is back-siphonage?
Backflow caused by negative pressure (i.e. a vacuum or partial vacuum) in a public water system or consumer potable water system. Back-siphonage may occur when there is a stoppage of water supply due to a nearby water main break, excessive fire hydrant usage or other high water demand event.
What is a backflow prevention assembly?
Backflow prevention assemblies protect our water supply from possible contamination by residential and commercial sources. Properly installed and maintained assemblies, devices, or methods protect against many conditions found in an onsite plumbing system. Muni Water recommends installing hose bib vacuum breakers on all hose bibs shown below in Figure 1. You can purchase vacuum breakers at most plumbing and hardware stores.
Figure 1. Vacuum Breaker home installation
What is a cross connection?
A cross-connection is an interconnection between drinking water from a public water system and a non-drinking water source (like a private groundwater well) through any actual or potential connection.
Why does cross-connection control matter?
Cross-connections may allow non-potable water to flow backward into the drinking water system, a process known as backflow. This may occur due to changes in water pressure and could allow contaminants to enter your home’s plumbing or the public water supply. Preventing backflow is essential to protecting public health and maintaining water quality.
Why am I hearing about this now?
In December 2023, the State Water Resources Control Board adopted updated regulations through the Cross-Connection Control Policy Handbook (CCCPH), which took effect on July 1, 2024. These updates require public water systems to enhance public education, conduct onsite hazard assessments, and ensure proper backflow protection is in place to protect the water distribution system.
How is Muni Water meeting the new requirements?
Our Cross-Connection Control Program has been updated to comply with the CCCPH. Our program includes:
Conducting and reviewing cross-connection assessments/surveys for all customers.
If it is determined that an onsite assessment is required, then the process will be determined on a case-by-case basis and the process will be communicated to the Muni Water account holder or property owner.
Verifying that required backflow prevention assemblies are properly installed, functioning correctly, and tested annually by certified Backflow Testers.
Providing public outreach and education on cross connection control and backflow prevention.
Do I have to do anything?
Yes. Fill out Muni Water’s Cross-Connection Assessment Survey to determine whether your plumbing or activities may pose a contamination risk to the public water system. If applicable, property owners are responsible for ensuring backflow prevention assemblies are properly installed, maintained and tested annually. The required testing must be performed by certified backflow prevention assembly tester. We will notify you if any action is required on your part.
How do I know if I have a cross-connection?
A cross-connection is any actual or potential link between your drinking water and a source of contamination, such as another water source on your property.
These are common in both residential and commercial settings. You may have a cross connection if your property includes any of the following:
Hose bibbs without backflow protection (e.g., vacuum breakers)
Toilet flush valves that are not properly air-gapped
Boilers or water heaters with makeup water connections
Landscape irrigation systems
Fire sprinkler systems
Private wells or alternate water supplies. This includes rainwater collection or water storage.
To protect your water quality and comply with local regulations, we recommend reviewing your plumbing system or consulting with a certified cross-connection specialist.
Which backflow prevention assemblies are approved?
Under most conditions, a lead-free reduced-pressure assembly is required. In some cases, a double-check assembly or airgap may be allowed based on service type or zone pressure conditions. The list of approved backflow prevention assemblies can be found on the USC Foundation for Cross-Contamination and Hydraulic Research page. Please contact our Backflow Prevention Team for guidance on selecting an appropriate device for your property at BackFlow@sanjoseca.gov or call (408) 277-3671.
What if I need more time to install my device?
We understand that coordinating the installation of a new device can be challenging. Requests for extensions will be evaluated on a case-by-case basis.
Does Muni Water inspect or test backflow assemblies?
Muni Water does not test customers’ backflow assemblies. Backflow testing and maintenance of backflow assemblies is the responsibility of the Muni Water account holder or property owner, who must hire a third-party Backflow Tester that is currently certified by the American Water Works Association. If it is determined that an onsite hazard assessment is required, then the process will be determined on a case-by-case basis and the process will be communicated to the Muni Water account holder or property owner.
