Backflow Preventer Leaking or Spraying Water? What to Do

Most people never think about the backflow preventer until it starts throwing water. It sits on a wall or in a patch of mulch beside the building, and for years it does its job without a sound. Then one morning there is a puddle at its base, or a fan of water coming from the side of the brass body, and the question is whether to worry.

You should take it seriously, but you do not need to panic. This guide explains what the device does, why it might be leaking or spraying, what to do in the first few minutes, what to avoid, and when a repair or a replacement is the right next step.

What a backflow preventer does

Your water supply pressure is what pushes water from the street into your building or your sprinkler system. If that pressure suddenly drops, because of a main break, a fire hydrant being opened, or heavy use nearby, water can try to flow the other way, back into the public supply. If it carries fertilizer from a lawn, chemicals from a boiler or other contaminants, that is a health risk to everyone on the line.

A backflow preventer is built to stop that. It contains check valves that close if the flow reverses, and some types have a relief port that opens to release water if the check valves cannot hold. The common types are:

• Pressure vacuum breaker, often used on irrigation, installed above the highest sprinkler head.
• Double check valve assembly, used where the hazard is lower, with two check valves in a row.
• Reduced pressure assembly, a more protective design with a relief valve between the check valves.

Which one your property needs depends on the hazard and your local water provider. We cover testing and record keeping in our guide to Houston backflow testing.

Why one leaks or sprays

A worn or fouled internal part

Check valves have rubber seals and springs, and these wear. Grit, sediment or a tiny piece of debris can hold one open slightly. In a reduced pressure assembly, a check valve that is not sealing can make the relief valve open and discharge water. That is the device doing what it was built to do, and it also tells you a repair is due.

A crack from freezing

Water inside an unprotected brass body expands when it freezes, and it can crack the body or break a fitting. The damage is often not visible until the water thaws and the assembly is used again, when it leaks or sprays. Houston does not freeze often, but when it does, bare pipes and exposed assemblies are the ones that fail.

A leaking fitting, union or test port

Not every leak is the device. The pipes and unions on either side can crack, loosen or move, and the small test ports on the body can weep. A leak at a joint may look like a failing assembly when the repair is simply the pipe.

Damaged pipe or supports around it

An assembly that is hanging on its pipes, or sitting on soil that has shifted, puts a strain on the connections. Tree roots, mowing and ground movement all take a toll. This is why the pipe and the device are looked at together.

A pressure surge

Water hammer or a sudden change in supply pressure can make some assemblies release a little water. A single short release after an event may not mean a fault, but repeated discharge does. If it happens often, it is worth finding the cause.

Age

An assembly installed many years ago, and never serviced, is more likely to have worn parts. Keeping a record of when it was tested and repaired helps you see when it is due.

What to do right now

1. Close the shutoff valves. There is usually one on each side of the assembly, with a handle that sits along the pipe when it is open and across it when it is closed. Turn both a quarter turn to stop the water. If the assembly serves an irrigation system, turn off the system at the controller as well.
2. Look at what is happening. Is the water coming from the relief port, a fitting, a crack in the body or the pipe? A photo helps when you call.
3. Check for freeze damage, if there has been a cold night. Cracks in the brass or white frost marks are a sign.
4. Keep the area safe. Water near an electrical box, a walkway or a driveway can be a hazard. Water spraying onto a wall can stain and damage it over time.
5. Tell the person responsible. If you rent or manage the property, the owner or property manager should know, because the assembly belongs to the property and the water provider may need to be told.
6. Call a plumber. A licensed plumber can find out whether it is a repair or a replacement, and whether the water provider needs a new test.

What not to do

• Do not cap, plug or tape over the relief port. It is a safety feature. Blocking it can let pressure build or defeat the device.
• Do not bypass the assembly with a pipe to keep the water on. That removes the protection and may break local rules.
• Do not remove it because it is leaking and you are not sure why.
• Do not bury it or enclose it in a box with no drain or room to test it.
• Do not keep running the system while it leaks, because the leak will get worse, and the water is going somewhere you do not want it.

Repair or replace

A plumber looks at the assembly, the damage and the age to advise you:

• Repair is sensible for worn seals or a single failed part on an assembly that is otherwise sound, and for leaking fittings and pipe around it.
• Replacement is the better choice when the body is cracked, parts are no longer available, the assembly is old and has failed more than once, or it was not installed correctly in the first place.
• Re-piping is often part of either job, because old unions and pipe next to a failed assembly are the next things to give way.

After a repair or replacement, many water providers want the assembly tested and the results filed. We explain what we do for these jobs on our page for backflow preventer installation and repair, and what the testing step involves in our guide to backflow testing. Property managers can see how this fits into regular maintenance on our property manager plumbing page.

How to protect it from cold

Freeze damage is avoidable, and most of the protection is simple:

• Wrap the exposed pipe with insulation and a weatherproof covering, as it comes out of the wall and runs to the assembly.
• Consider an insulated cover or enclosure for the assembly, which is made for the purpose and still lets the assembly be reached for testing.
• Drain the irrigation system before a hard freeze if the assembly can be drained, or ask your plumber how to do it for your type.
• Do not wrap it so tightly that the test ports or the relief port are blocked.

A leak that is not the assembly

Sometimes the wet patch near the assembly is not coming from it at all. A leak in the supply line can surface nearby, and a water bill that jumps with no visible cause is a clue. We explain how to check in what to do when your water bill goes up and nothing is leaking. Our page on water line repair covers leaks in the line that feeds the property.

Keep records

Keep a folder, paper or digital, with the date and result of each test, any repair, the type and size of the assembly, and the tag details. Your water provider may ask for it, and it helps the next plumber understand the history. If you manage several properties, a simple list showing which assemblies are due saves time and avoids notices.

Royal Flush Affordable Plumbing is licensed and insured, and works under Texas Responsible Master Plumber License RMPL #42403. The price is agreed before the work begins.

Royal Flush Affordable Plumbing

Licensed Houston plumbers since 2007. Residential, commercial and industrial plumbing, 24 hours a day, with upfront pricing and no hidden charges.