(408) 978-3093

Backflow Preventer Installation and Replacement in San Jose, CA

A backflow preventer keeps irrigation, fire sprinkler and building water from flowing back into the public supply. We install, replace and repair them for San Jose homes, HOAs and businesses, with a written fixed price after a site visit. Our certified testers test every device we install and file the results with your water supplier.

  • Google 4.9130+ reviews
  • Licensed C-36 · C-20 · ACSLB License #1101278
  • 1-year labor warranty24/7 service since 1986
Call (408) 978-3093See prices
A smiling CPI Service plumber with a toolbox next to a CPI Service van in a San Jose driveway

Get a Free Estimate

Takes about 30 seconds. No obligation.

What do you need help with?

Google 4.9 · 130+ reviews · CSLB #1101278 · BBB A+

Or call (408) 978-3093, 24/7, or book a time online.

By submitting, you agree we may call or text this number, including automated messages, about your request. Msg & data rates may apply. Reply STOP to opt out. Privacy policy

Backflow Services in San Jose

One call covers the whole job: choosing the right assembly, installing or replacing it, testing it and filing the results.

  • New backflow preventer installation

    Devices for new irrigation systems, fire sprinklers, commercial kitchens, boilers and other connections your water supplier says need protection.

  • Backflow preventer replacement

    Failed, leaking, stolen or obsolete assemblies replaced with an approved model of the right type and size, then tested.

  • Repair and rebuilds

    Failed a test? Many assemblies can be repaired with new checks, seals or a relief valve instead of being replaced.

  • Certified annual testing

    Our certified backflow testers test assemblies and send the results to your water supplier by its deadline.

  • Enclosures and theft protection

    Locking cages and insulated covers protect brass assemblies from theft, damage and the occasional freezing night.

  • Irrigation backflow devices

    Pressure vacuum breakers and other devices that keep fertilizer and yard water out of your drinking water.

When You Need a New or Replacement Backflow Preventer

These are the usual reasons San Jose property owners call us about backflow devices.

Get a free estimate
  • Your water supplier sent a notice

    A letter saying a connection needs protection, or that a device is missing, overdue for testing or failed its test.

  • The device failed its annual test

    If a repair isn't practical or parts aren't available for an older model, the assembly needs replacing.

  • Water spraying or dripping from the device

    A reduced pressure assembly that keeps discharging water from its relief valve has an internal problem.

  • A stolen or damaged assembly

    Brass backflow assemblies are a target for theft. A missing device leaves the water off, or the system unprotected.

  • New irrigation, fire sprinklers or equipment

    Adding a sprinkler system, a commercial kitchen, a boiler or a second water service usually requires a backflow preventer.

  • A remodel or change of use

    Converting a home office to a business, adding a pool fill or changing a building's use can change what protection is required.

What a Backflow Preventer Does

Water in the street main is under pressure, and that pressure normally keeps it flowing into your property. When the pressure drops, for example during a main break or when a fire hydrant is opened nearby, water can reverse direction. That’s backsiphonage. Backpressure is the opposite problem: a pump, boiler or elevated tank on your side pushes water back toward the main.

Either way, whatever is connected to your plumbing can end up in the drinking water: fertilizer and yard water from irrigation lines, stagnant water from fire sprinkler pipes, chemicals from commercial equipment. A backflow preventer is a mechanical assembly that lets water flow in only one direction and blocks that reverse flow.

Types of Backflow Preventers

Device How it protects Typical use
Reduced pressure (RP) assembly Two check valves plus a relief valve that dumps water if they leak High-hazard connections: commercial kitchens, medical offices, boilers, some irrigation
Double check (DC) assembly Two independent check valves Lower-hazard connections, many fire sprinkler systems
Pressure vacuum breaker (PVB) Check valve plus an air inlet that opens when pressure drops Residential irrigation (backsiphonage only)
Atmospheric vacuum breaker (AVB) Air inlet on a single zone, no shutoff downstream Hose bibs, single irrigation zones

Your water supplier decides which type is required, based on the hazard. Installing the wrong type, or the right type in the wrong place, means a failed inspection and paying twice, so we confirm the requirement before ordering parts.

Replacement or Repair?

A backflow assembly that fails its annual test isn’t automatically scrap. Most testable assemblies are designed to be rebuilt: our technicians replace the check valves, springs, rubber parts or relief valve, and the tester retests it on the spot. Replacement makes sense when the model is obsolete and parts aren’t available, the body is cracked or frozen, the device was stolen, or the existing assembly is the wrong type for the hazard. We’ll tell you which way is cheaper before we start.

Installation Done Right

A good installation makes every future test and repair easier:

  • Approved assemblies only, of the type and size your supplier requires.
  • Test cocks and shutoffs placed where a tester can reach them.
  • Proper clearance and drainage, especially for RP assemblies, which must sit above ground.
  • Protection with a locking enclosure or insulated cover where theft or weather is a risk.
  • Testing and paperwork handled by our own certified testers, so the job is finished when we leave.

Sources

Checked October 2026.

How Much Does a Backflow Preventer Cost in San Jose?

The price depends mostly on the type and size of the assembly and on the piping around it. A small irrigation device is a short job; a large reduced pressure assembly for a commercial building is a bigger project. After a site visit we give you a written fixed price that includes installation and the first test.

Typical backflow preventer installation prices in San Jose, installed, in US dollars. Checked October 2026.
ServiceTypical San Jose price (USD)
Flat-rate pricingTypically based on $150–$250 per hour, plus parts and drive time
After-hours flat-rate pricingTypically based on $200–$300 per hour, plus parts and drive time, with a minimum charge
Inspection feeWaived for service plan members$59

What affects the price

  • Type of assembly. Reduced pressure (RP) assemblies cost more than double checks or vacuum breakers.
  • Size. A 3/4-inch residential device and a 4-inch commercial assembly are very different jobs.
  • Piping changes. Moving a device above ground, adding shutoffs or rerouting pipe adds time and material.
  • Enclosure. A locking cage or insulated cover is an optional add-on.
  • Water shutdown. Commercial and HOA work may need after-hours shutdowns, billed at emergency rates.

Most repairs are quoted as a fixed price before we start. Ranges are typical for San Jose and the South Bay and don't include current specials.

How Backflow Installation Works

  1. Review the requirement

    Send us your water supplier's notice, or tell us what you're adding. We confirm the hazard level and which assembly is required.

  2. Site visit and price

    We check the service line, space, drainage and access, then give you a written fixed price.

  3. Install or replace

    We install an approved assembly of the right type and size, with shutoffs and test cocks where they can be reached.

  4. Test and certify

    Our certified tester tests the new assembly as soon as it's installed.

  5. File the paperwork

    We send the test results to your water supplier and give you a copy for your records.

  6. Annual reminders

    We can test it every year so you stay ahead of your supplier's deadline.

Backflow Rules for San Jose Property Owners

Who asks for backflow protection, and how often it's tested, depends on your water supplier and on California's cross-connection rules.

  • Your water supplier sets the requirement

    Most of San Jose is served by San Jose Water; parts of the city, such as North San Jose, Evergreen and Edenvale, are served by San José Municipal Water. Your supplier decides which connections need a device and tracks the test results.

  • California's cross-connection rules

    Water suppliers follow the State Water Board's Cross-Connection Control Policy Handbook, which took effect in 2024, and require approved assemblies to be tested at least once a year by a certified tester.

  • Irrigation and fire sprinklers

    Landscape irrigation and fire sprinkler systems are the most common reasons San Jose homes, HOAs and businesses have a backflow device.

  • Commercial and multi-unit buildings

    Restaurants, medical and dental offices, car washes, boilers and buildings with several water services usually need reduced pressure assemblies.

  • Theft and vandalism

    Brass assemblies near the street are a theft target across the Bay Area. A locking enclosure is far cheaper than a replacement.

  • Above-ground installation

    Reduced pressure assemblies discharge water from a relief valve, so they're installed above ground where the water can drain, not in a pit.

Neighborhoods we serve: Downtown San Jose · Willow Glen · East San Jose · South San Jose · Evergreen · Cambrian Park · West San Jose · Berryessa · North San Jose · Blossom Valley

Current Specials

Save on your visit. Mention the offer when you book.

What Our Customers Say

Google 4.9 from 130+ reviews: read more →See photos of our work →

  • I have called on CPI multiple times. The first time was a critical emergency to replace hot & cold lines to an outside building which failed due to age and natural deterioration. The second and third times were minor interior jobs. Today they replaced and upgraded the main line from the street to our home. Next, I plan to have them take care of everything for a new home we’re planning to build. These guys are awesome. They can handle any size job. Prices are fair. I like Matt a lot. Attention to detail and quality is fantastic. Highly recommend.

    T. S.Yelp review

  • Quality work, fair price, very responsive. Our go to company in Bay Area.

    A. C.Google review

  • Prompt response, polite, knowledgeable. Good at explaining options and following through until solved.

    Pauline M.Google review

Backflow Preventer Installation FAQs

What is a backflow preventer?

A backflow preventer is a valve assembly that lets water flow only one way, from the public water system into your property. It stops irrigation water, chemicals or building water from being pulled or pushed back into the drinking water supply when pressure drops.

Do I need a backflow preventer at my home?

Most San Jose homes need one only for certain connections, most often landscape irrigation or fire sprinklers. If your water supplier sent you a notice, it will say what's required; send it to us and we'll take care of it.

What's the difference between an RP and a double check?

A double check assembly has two check valves and is used for lower-hazard connections. A reduced pressure (RP) assembly adds a relief valve between the checks that opens and dumps water if they leak, and is required for higher-hazard connections.

How often does a backflow preventer have to be tested?

Water suppliers in California require testable assemblies to be tested at least once a year, and after installation or repair, by a certified tester. We test, file the results with your supplier and can remind you each year.

Can a failed backflow preventer be repaired?

Often, yes. Worn checks, springs, seals and relief valves can be replaced, and the assembly retested. If the model is obsolete or the body is damaged, replacement is the better choice.

Do you install backflow preventers for businesses and HOAs?

Yes. We install, replace, repair and test residential, commercial, HOA and fire sprinkler assemblies, and we schedule shutdowns around your tenants or business hours.

Helpful Guides

Serving San Jose and the South Bay

Our shop is at 2880 Aiello Dr in San Jose. We provide backflow preventer installation across the city and nearby South Bay and Peninsula communities. See our full service area.

Content and prices reviewed October 2026.

Need backflow preventer installation in San Jose? We're here 24/7.

Get a Free Estimate(408) 978-3093Book online