Backflow Preventer Replacement or Repair? How To Decide

If your backflow preventer isn't performing as well as it could, you may be forced to make a difficult decision. Should you repair or replace it? A backflow preventer replacement is sometimes, but not always, the more cost-effective choice.

With proper maintenance and annual testing, backflow prevention assemblies can last for many years. But backflow preventers have internal seals, springs and moving parts that are subject to clogging, wear or fatigue.

We got advice from Sean Cleary, vice president of the International Association of Plumbing and Mechanical Officials (IAPMO) and the Backflow Prevention Institute® (BPI). Cleary has been in the backflow business for more than 40 years and, as a licensed master plumber, he's worked in all aspects of the plumbing and mechanical industries.

Let's take a look at some of the factors he says you must consider when deciding whether to repair or replace your backflow preventer.

Valve Size and Backflow Preventer Cost

"One of the first things to consider is the size of your valve," Cleary said. "A lot of times it's simply easier — and more affordable — to replace a smaller valve that's bad. I know of a few plumbing contractors who stock their service vans with a half-inch, three-quarter and one-inch assemblies, and if they have a failure while they're doing a test, it's more economical for the customer to swap the valve out."

Sizing the assembly correctly also matters beyond cost, because an undersized unit can cause a water pressure drop across the system.

Cleary also says it can be tough to get parts for an assembly, depending on your location. That too can factor into the decision of replacing a smaller valve rather than repairing it.

When it comes to a larger valve, Cleary said there are other things to consider. "The backflow preventer cost is so much more for a larger assembly than for a smaller one," Cleary says. "You really have to look at the condition of the valve."

Whether it's an isolation ball valve on a smaller assembly or a full reduced pressure zone device on a larger line, the size of the unit drives both the labor costs and the materials involved. The device type is a big driver of price too: RPZ, PVB and DCVA assemblies each carry different costs, and a preventer typically runs $200 to $1,000 installed, though sprinkler-system units tend to land in the $100 to $600 range and simple hose models cost as little as $3 to $100.

Cleary says even if you can repair a larger valve, it may not mean that you should. "You may have a 35-year-old valve with its epoxy coating flaking off, and even though it may only cost a few hundred dollars to repair, you may be better off installing a more modern valve that will be less expensive to maintain over the years," Cleary says. "Today's backflow preventers are shorter, they're lighter, there are fewer parts and they're easier to maintain."

Condition of Your Valve

When you're trying to decide if you should replace backflow preventer parts or the whole assembly, the condition of your backflow preventer is a major consideration. According to Sean Cleary, if you have a smaller valve whose checks are brittle and ready to crack, you should consider replacing it. "If I have to replace two checks, along with the rest of the rubber parts and everything else, it may be less expensive to replace the valves."

Another factor to consider with smaller valves is where it's been installed. Take swimming pool equipment rooms, for instance. "The environment in these rooms may cause valve handles to rust away and affect the assembly body itself," Cleary says. When you do open things up, it's worth inspecting the surrounding plumbing for corrosion or damage at the same time.

In addition to the epoxy coating flaking off a larger valve, you should also consider the interior conditions of the valve — the valve make-up. "If you have a larger valve with the epoxy coating coming off, the O-ring won't make the proper seal. There's no way to fix the epoxy coating, and the water is going to start eating at the valve body itself," Cleary said.

Cleary adds that you should also pay attention to the shut-off valves on larger backflow preventers. If they're not holding properly, you have to look at what's going on internally. "If you have a 30-year-old valve that needs thousands of dollars in repairs, it's probably time to replace it."

The goal is to eliminate the risk of a cross-connection. Any temporary or permanent connection between a public water supply or the customer's potable water system and any source or system containing nonpotable water or other substances can be devastating.

Consistent backflow testing is what surfaces these problems before they reach the drinking water. In many areas, annual testing isn't optional; it's required to stay in compliance, and each test is estimated to cost somewhere between $30 and $300 per device.

Your Valve's Location

Location is another factor in your decision to repair or complete a backflow replacement. Backflow preventers in an outdoor, above-ground enclosure are easier to work on. "More valves are going in enclosures, more valves are going above ground, and to be honest, that's where they belong," Cleary mentioned. Location also carries a freeze risk worth weighing: an outdoor preventer left unprotected can crack and leak once temperatures drop below freezing.

A properly designed enclosure will have removable panels and perhaps a removable roof to make it much easier to test, repair or replace your backflow preventer. "Placing an approved backflow assembly in an outdoor enclosure makes it easier to keep up with annual testing and repairs because it's more accessible," Cleary added. Placing your backflow preventer in an enclosure also helps to minimize flood risks.

Ask the water jurisdiction to provide a standard detail for outdoor, above-ground backflow preventer installations. If they don't have one, grab a sample one here from our Standard Details Guide.

Before you replace a unit, check your local rules, since plumbing codes govern replacement requirements and most jurisdictions require certified testing once the new assembly is in. A permit is often part of the process as well, sometimes costing around $50.

If you're specifying industrial equipment, check out our Guide to Industrial Enclosure Design for an overview of the main design considerations including size and strength, climate control, access and maintenance.