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How To Winterize Your Backflow Preventer

You can protect your backflow preventer from freezing

Why Homeowners Should Winterize Their Backflow Preventers When Possible

The Maintenance Shop winterizes backflow preventers during our sprinkler blowout at each property, but there are reasons why we advise homeowners to prepare their backflows themselves if at all possible before we get there.

There are over 250,000 homes, businesses, farms, restaurants, churches, etc., in the Treasure Valley that need their sprinklers blown out each fall, and with the continued growth in the valley that number is going to steadily rise. In 2018 there were over 5,000 building permits issued in Ada and Canyon county combined. Unfortunately, there are not enough QUALIFIED sprinkler blowout technicians to meet this demand, which is why some homeowners find they are waiting up to 3 weeks for a sprinkler blowout. We put emphasis on "QUALIFIED" technicians because every spring we get a heavy workload doing repairs on systems from previous season sprinkler blowouts being done by those out to make a lot of quick cash that really don't know what they are doing, and then can't be found again. Nearly half of these repairs are damaged backflow preventers because the technician either didn't follow the steps we are going to show you below, or didn't do it properly. They are able to do this because of the high demand and lack of technicians. Out of desperation homeowners will flag someone down pulling a compressor down their street, or call a number on a sign posted on a street corner without really finding out who they are. ALWAYS ask for your own protection who they work for, and if they are licensed or work for a licensed company.

The weather here in the Treasure Valley is unpredictable to say the least. Underground sprinkler systems are usually quite safe even into early or mid-December or sometimes into January if we haven't had several days of extreme cold temperatures in the teens or lower. We have proven this several times doing sprinkler blowouts when the outside temperature was 13 degrees with snow on the ground, but the ground temperature itself at the level where piping is was in the mid-30's. Snow is actually a good insulator. HOWEVER, backflow preventers, ESPECIALLY ones that are above ground will not fair well even if the temperature get down to the mid 20's and stays there for several hours. A slow drop to freezing won't be a problem, but a continual drop that stays there for a while could cause a backflow preventer to freeze and crack.

The older backflow preveters are comprised of lead and brass, which will expand some in the cold before cracking. The new lead-free backflow preventers are more fragile. With the rising replacement cost of backflow preventers, and especially since Double Check Backflow Preventers can no longer be installed on sprinkler systems in Idaho, we need to protect our current backflow preventers the best we can.

You can easily winterize your backflow preventer to protect it from freezing

We suggest you winterize your backflow preventer as soon as you are finished watering for the season. Don't put it off until it starts getting colder. You will have no use for it again until Spring.

The procedures we have put together below are exactly what we do when we come to your home or business to blow out your sprinkler system. The steps are easy to follow, and not only will it give you piece of mind, but it will actually save us valuable time. If you choose to winterize your backflow yourself, we will always check it during the sprinkler blowout to make sure it is was done correctly, however, please follow the directions carefully to make sure no damage occurs. We have had a few customers here and there that attempted to winterize their backflow preventer but missed one or more crucial steps and damage occurred.

Backflow Preventer Winterization instructions

Look at the images below and choose the picture that best matches the backflow preventer you own. There are different varieties, but most look simiiar to each other. The PVB's and RP's will always be above ground if they are installed correctly, and the majority of the time the DC's will be below ground, although on rare occassions we have found them above ground. Click on the picture and it will open in another screen to full size where you can print the image. We suggest you put the instructions next to your timer where you have easy access to it when you need it.

NOTE: If you do not know the difference between the main and drain valves, try turning one valve counter-clockwise. If water starts coming out and or filling up up the pipe in the ground it is the drain. If it doesn't move, it is the main. Shut the main valve by turning clockwise and then open the drain by turning counter-clockwise. For future reference, take a permanent marker and right a "M" for main and a "D" for drain inside the tube near the top.  That way you will remember which is which, and it also helps us. Never right on the lid because the lids can get switched easily if you have two pipes in the ground for your valves instead of one larger pipe.

If you have trouble physically being able to carry out any of the instructions below please enlist the help of a family member or neighbor.


PVB Backflow Assembly winterization instructions

Pressure Vacuum Breaker (PVB) Winterization Instructions

Double Check Backflow winterizing instructions

Double Check Valve Assembly (DC) Winterization Instructions

Reduced Pressure Principle Backflow Assembly winterizing instructions

Reduced Pressure Principle Backflow Assembly (RP) Winterization Instructions


Pump winterizing instructions

Pump Winterization Instructions

Irrigation filter winterizing instructions

Irrigation Filter Winterization Instructions

Instructions to relieve pressure on electronic valves

Electronic Valves Pressure Relief