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how to winterize your irrigation system using the blow out method

Winterization is an important part of maintaining a properly running lawn sprinkler system. Where you live plays a big part in which steps you will need to follow. In this how-to guide to winterization, we will take a look at the steps involved in winterizing your sprinkler system in a cold climate. As a part of that, we will examine the "blow out method" for removing the water from pipes and sprinklers. When you have finished reading this article, you will have the knowledge necessary to successfully winterize your lawn sprinkler system - and you'll understand why most experts agree that a sprinkler system blow out is the most recommended method to use.

Step One: Turn Off The Water

First things first: when the time to winterize your irrigation system rolls around, you'll need to shut off the water at the main valve before doing anything else. By necessity, the shut off valve for your sprinkler system needs to be located in a place where it can't freeze up; this should have been done when the system was originally installed.

Step Two: Shut Down The Controller

Here's where things get a little less cut-and-dry. Automatic irrigation systems have a controller - or timer - that regulates when they turn on and off. Depending on what kind of controller you have, you may either choose to set it to "rain mode" or disconnect the power from it altogether.

Please note that you can always buy a more up-to-date, efficient controller or timer to save yourself a lot of time and money in the long run. offers the best selection and most competitive prices for lawn sprinkler system controllers on the market today.

Solid State Controllers

A solid state controller usually have digital time displays and generally use up a lot less electricity and power than their mechanical counterparts. Disconnecting the power from your sprinkler system controller means having to reset all of its associated settings when spring returns - not necessarily the simplest task in the world.

Solid state controllers tend to use very little electricity, though, so leaving them on - but in "rain mode" - will not cause a major spike in your electric bill. Therefore, if you have a solid state digital controller, use the "rain mode" setting and save yourself a lot of frustration down the line.

"Rain mode" means that your controller stays on, maintaining its settings, programming and keeping the time - but the valves simply don't come on. They can save you a great deal of time when it comes to winterization.

Mechanical Controllers

Mechanical sprinkler system controllers can be identified quite easily; they typically have a dial on them similar to one found on an analog clock. These machines do use up a lot of electricity when compared to solid state controllers. Most people find the cost of keeping mechanical controllers on throughout the winter overly prohibitive.

Instead of using "rain mode," then, it makes sense to turn off the power to a mechanical controller for optimal winterization performance. One more thing: if you have a pump wired to your mechanical controller, disconnect it. This can help eliminate the risk of the controller inadvertently kicking in and damaging the pump.

Step Three: Remove The Backflow Preventer And Take Care Of Risers

Next, you will need to remove the backflow preventer from your lawn sprinkler system. Once it's removed, drain all the water from it and store it someplace safe. Although you can always reinstall it once it's drained, that's usually a task best kept for the springtime.

While there's a chance that you'll be able to siphon water out of your irrigation system's risers, chances are that you'll have to pump it out. If so, a wet/dry shop vacuum is your best option; use duct tape to make the hose narrow enough to work properly.

Valves that are installed above ground should be drained of water and stored somewhere safe. Some people choose to use pipe heating cables on their backflow preventers and above ground valves. Keep in mind, though, that even when used properly such arrangements can fall victim to power outages and serious damages to your irrigation system can occur.

Removing A Backflow Preventer

As noted previously, removing your irrigation system's backflow preventer and storing it for the season is a smart move when you're completing the other steps involved in winterization. How do you remove a backflow preventer, though? With any luck, the one that you have is held in place with union connections. In this case, you'll just need to uncouple them on either end of the backflow preventer, just before the bends in the piping. Once it's removed, storing it will be simple. You can use insulation on the exposed ends of the pipe to keep them safe from harm - and to keep critters and debris from inadvertently getting in.

If you don't have union connections in place, though, you're in for a little bit more work. The people who have the biggest trouble removing their backflow preventers are the ones whose system doesn't use union connections. In this case, you'll have to cut the backflow preventer out manually. It's definitely more work, but the good news is that once that's done, it's done. When spring rolls back around, you can reinstall the backflow preventer for your irrigation system using union connections; the next time you need to winterize your lawn sprinkler system, it will be considerably easier.

Step Four: Removing Water From The Pipes And Sprinklers

Now comes the most important step of the winterization process: removing all of the water from the system's pipes and sprinklers so that it doesn't freeze, expand and burst everything. There are a few different ways of approaching the problem: using a shop vacuum to suck all of the water out (a very time-consuming and aggravating process), draining the water out via the system's drain valves or using air to blow all of the water out (also known as a sprinkler system blow out). Since using a shop vac is so inefficient, we will only take closer looks at how to use the drain valve method or the blow out sprinkler system method.

The Blow Out Method

Although we will be outlining how a sprinkler system blow out works, it is best to have a professional perform this kind of work for you. In fact, hiring a professional to conduct winterization work is the best way to go, if possible.

CAUTION! WEAR PROPER EYE PROTECTION! Extreme care must be taken when blowing out the system to avoid excessive pressure which can damage valves or sprinkler pipe or cause physical injury due to flying debris. Do not stand over any irrigation components (pipes, sprinklers, and valves) during air blow out. Air pressure must not exceed 50 pounds per square inch (psi) for systems with polyethylene piping, and 80 psi for systems with PVC piping.

  • Get The Right Equipment - To conduct a sprinkler system blow out, you will need a very large air compressor. To obtain proper air volume, you will need to rent or buy a compressor capable of providing 80 to 100 cubic feet per minute (CFM) of air volume. At minimum, you should use a 50 cubic feet per minute compressor to get the job done right. Anything smaller will make the job inefficient - and may even make it impossible. Make sure the compressor has a pressure regulator valve with an accurate gauge. If possible, try renting different sizes and kinds of air compressors until finding one that works the best - then purchase it so you don't have to rent it again every time you winterize.

    If the appropriate air compressor is not available, please call an irrigation contractor. Do not try to use an air compressor with high pressure (120 psi) and low volume to evacuate water from the system. It is not an acceptable practice to allow the compressor to fill the holding tank of the compressor and the closed mainline with high pressure air, hoping the surge of excess pressure will compensate for the lack of compressor size and blow the line clean upon opening the sprinkler control valve. This is a dangerous practice that places very severe stresses on all of the components of the system. Do not run the compressor without at least one sprinkler control valve open. This lessens the chance that the system could over pressurize. It is a common misbelief that if the system can withstand 120 psi of water pressure, similar air pressure will not damage the system. This is not true! The viscosity of air is much lower than water, generating much higher stresses that can cause severe damage to the system.

  • Remove The Backflow Preventer - Most likely (and preferably) your backflow preventer will be located just after the irrigation shut off valve for your lawn sprinkler system. If you have an anti-siphon valve, remove the whole valve.

  • Connect The Air Compressor - On the downstream side of the system, connect the air compressor to the backflow preventer riser.

  • Turn On The Valves - Always turn on your valves one by one, using the automatic controller, when you blow out sprinkler system. Begin with the last valve - or the one at the highest elevation. Open manual valves by hand. If you've removed the anti-siphon valves, you will need to connect the compressor hose to the downstream part of the valve risers.

  • Turn On The Air Compressor - With this step, taking your time is key! Gradually increase the pressure without letting it exceed 50 psi. If the air coming out of the air compressor becomes dangerously hot, you may need to install a length of hose between it and sprinkler system connection, so be prepared.

  • Blow The Water Out - Keeping a close eye on the air pressure and temperature, allow the water to blow out. The first valve will generally take the longest; after that, things should proceed rather quickly. Don't allow air to blow out any longer than necessary - i.e., as soon as the water has been effectively blown out, turn off the air compressor.

  • Move On To The Next Valve - Turn off the valve that you just worked on, and proceed to the next one following the same steps. Repeat the same sprinkler system blow out as outlined above on each of valve circuits; with anti-siphon valves, remember to move the air compressor on to the next valve riser.

  • Repeat The Entire Process - For optimal results, perform the exact same blow out sprinkler system process again. Warning: do not turn off all the valves when the compressor is running - it could blow up your lawn sprinkler system.

  • Blow Out Main Line Section - If your irrigation system has a mainline section that is upstream from the backflow preventer, hook up your air compressor to the blow out fitting near the sprinkler system shut off valve; blow out the water through the backflow preventer riser.

  • Tie Up Loose Ends - When the sprinkler system blow out is complete, set the automatic controller to "rain mode" or disconnect power from it. Place threaded caps over the anti-siphon valve fittings, backflow preventer risers - over anything that might allow pests or garbage to get in.

  • Turn the Controller / Timer Off

Increase pressure gradually!
It is extremely important not to exceed 50psi. Use CAUTION during this step

Connecting The Air Compressor To The Backflow Preventer Riser

If you've never connected an air compressor to the backflow preventer riser on your irrigation system before, it's important to learn. Otherwise, winterization via blowing out the system will be impossible. Most of the time, you just need to look for a hose tap, quick coupler or hose bib that is after your irrigation shutoff valve and backflow preventer. You can connect your air compressor hose to this for the easiest, most straightforward time. If there is no tap or other convenient option present, install a tee fitting just past the main line. Then put a threaded metal nipple and cap on the extra leg; you can use this as a connection to the air hose. You'll want to use a metal nipple and cap because the pipe can get very hot at the point of the connection due to the speed at which the air is being blown.

Connecting the compressor air hose to the nipple and cap end of the tee fitting isn't always a cut and dry procedure; it usually requires a bit of ingenuity, and the precise size fitting that you will need to connect the compressor hose to the tee fitting depends on the model of air compressor you're using and other variables. It's safe to assume that a standard fitting won't do the job; a bit of trial and error is usually necessary. Once the right fitting is found, though, it's as simple as screwing the air compressor hose onto the tee fitting. The threads from the tee fitting should fit with the threads on the metal nipple - that will be your ultimate goal, anyway.

Otherwise, another way of going about this process is unscrewing one of the test cocks and threading a male air hose fitting onto it. Simply attach the female end of the air hose to the male end of the line and you'll be good to go. A bit of trial and error is something necessary when the time to winterize rolls around, so don't be surprised if you have to make several trips to the hardware store to get everything working the right way. Be sure to organize all of the equipment and tools that you use to make the process easier next year.

A Note About Backflow Preventers

Whether you live in a temperate or a cold climate, you can save yourself a lot of hassle - and make winterization much easier - by insulating your irrigation system's backflow preventer. In cold climates, occasional late and early season freezes occur and can damage your equipment. Using a small amount of self-sticking foam insulating tape - without blocking the drain outlets or the air vents - should be sufficient. Otherwise, try using some R-11 fiberglass insulation. Wrap it around the backflow preventer, then use duct tape to secure a plastic bag around the whole thing. Don't secure it too tightly - just tight enough to keep it from blowing off.

Practice Makes Perfect

As outlined above, it is easy to see that winterizing your irrigation system doesn't have to be an impossible task. Doing it yourself can save you a great deal of money, and with every passing season you will become more skilled at it. Having the right equipment and parts can also help tremendously; you can find the best controllers/timers, for example, by visiting Remember, also, that once you've insulated all of your pipes and backflow preventers properly, you will be set for some time and won't need to repeat the process every single year.

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