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Backflow Program

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Typical installation of an RP backflow device located just downstream of a water meter

Backflow Program

What is a backflow device?

FPUD maintains over 1,200 backflow devices throughout our service area.  These devices are located at the boundary between the FPUD system of public water mains and private plumbing systems.  The purpose of a backflow device is to prevent water in private water lines from flowing back into the public water system.  Backflow devices in FPUD's system are reduced pressure assemblies (RP) and double check assemblies (DC).  To simplify and streamline maintenance, FPUD is in the process of phasing out DC devices.   

Why does my water service have a backflow device?

Plumbing codes and state regulations require backflow devices to be installed at public water system connections for many reasons (please see our administrative code, section 19.22 for details on FPUD requirements).  The most common installations are found on agricultural properties (or were ag properties at one time) and on properties that have an auxiliary water supply such as a well or a recycled water system.  The reason that agricultural properties are required to have a backflow device is that it is common for ag sites to have infrastructure within their water systems that may use drinking water contaminants such as fertilizer injectors.  As a result, state law requires the installation of backflow devices on water services that serve agricultural properties.  Properties that have wells or recycled water systems on their property (or that have irrigation or ponds served by wells) are also required to have backflow devices installed at their public water system connection(s), as there is a possibility that lines fed by the public water system could be cross connected with lines fed by the well or auxiliary water supply.  This requirement is also mandated by state law.  

What does a backflow device do?

In short, a backflow device prevents water in private water systems from entering the public water system.  This can occur in instances such as a emergency water leak (vehicle strikes a fire hydrant) that lead to erratic flow conditions within the public water mains (back-flow) or if a private water system has equipment such as a pump (for example on a well) that causes pressures in the private lines to exceed the pressures in the public water system (back-pressure).  One of the most important responsibilites of water utilities is to provide safe, clean drinking water, so it is very important that we enforce backflow requirements when they are deemed necessary.

Why do I get charged a monthly fee to maintain the backflow device at my meter?

Backflow devices, like all mechanical equipment require periodic inspection and maintenance to ensure they are functioning properly.  Because you pay FPUD to maintain your backflow, it is the sole responsibility of FPUD to inspect and maintain the device.  All backflow devices in the FPUD service area are inspected annually (per state law), and at times they need repairs or replacement.  The monthly charge you see on your bill pays for these services.  Because FPUD is able to buy parts and equipment in bulk, and we have locally based staff to perform this maintenance on a large scale, it is very likely that we are able to maintain a backflow device at a lower cost than if a property owner had to pay a private contractor to annually test and maintain/repair/replace a privately owned device.

My property is no longer agricultural and I don't have an auxiliary water supply, can I have the backflow installed at my meter removed, and stop being charged the monthly maintenance fee?

Potentially.  If your meter has a backflow, but your property does not have any conditions that require the installation of a backflow (examples; the property is no longer an agricultural property or you do not have an auxiliary water supply), you may be able to have the device removed and stop being charged the monthly fee for maintenance.  If you would like to initiate this process, the first step is to fill out the "Backflow Questionnaire" pdf at the bottom of this page, and return to the District offices either by mail or email ( with the note "C/O Backflow Removal Request".  Our staff will initiate the review process and follow up with you.  

I want to get an agricultural water rate and I see that I need to have a backflow installed.  What do I need to do?  Will FPUD install it for me?

New installations of backflow devices that are not associated with the installation of a new water service are the sole responsibility of the property owner.  Please review the "Backflow Installation Specification" pdf provided below.  This work is usually done by a plumber .  Unfortunately, the District is not able to make recommendations for private contractors to do the work.  Make sure you communicate with whomever you hire that the specific device listed in the specification is used in the installation, and that all configurations of the installation match the specification (fittings, layout of runs of pipe, etc).  The reason there is very little flexibility in the installation of these devices is that once they pass inspection, testing and maintenance becomes the responsibility of the District, and standardized configurations and parts aid the District streamline this work and keep maintenance costs down.  If your plumber has questions regarding a backflow installation have them contact the Engineering Department directly at (760)728-1125, (then press 5).  Once the device has been installed, contact the District to schedule an inspection.  After the device passes inspection FPUD will take ownership of the device, track and perform ongoing testing/maintenance, and you will see a charge on your monthly bill "Backflow".  

If you have any additional questions, please feel free to contact the Engineering Department by phone at (760)728-1125 (then press 5) or by email at

Backflow Prevention Questionnaire_2020.pdfBackflow Installation Specification 2024.1.22.pdf