How to winterize your sprinkler system
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How to Winterize Your Sprinkler System

Learn how to perform this essential winter maintenance to protect your sprinkler system from frozen water pipes.

The majority of the year, you depend on your sprinklers to keep your lawn looking wonderful, but when autumn arrives, you need to spend some time to empty and insulate them so they’ll be just as dependable in the spring. If you don’t properly winterize your sprinkler system, any water that is still in the pipes when the cold weather arrives will freeze, expand, and break, potentially resulting in expensive damage.

Step 1: Turn off the main water supply and if present, the backflow preventer. 

First, turn off the main water supply, often found near your water meter. Shut off the backflow preventer valves as well if your sprinkler has manual drain valves. A backflow device keeps pressured, potentially polluted water from mingling with the potable water supply and is often placed close to the water main where the sprinkler water is extracted. Your system might not have a backflow device if you don’t use potable water for irrigation, but if it does, you can turn it off using two valve shut-off handles on the various pipes that feed into the device. Use pliers if the valves are too tight to turn by hand; otherwise, just turn these rectangular handles one-quarter to one-half turn counterclockwise.

Step 2: Drain any water remaining in the irrigation system

  • If your sprinkler system uses an automatic drain valve, this spring-loaded drain valve will open every time the system shuts off because there is little to no water pressure running through the lines to press and close the valves. But this draining won’t release water trapped inside the valves themselves, so on each valve of the sprinkler system, locate the solenoid—which typically looks like a PVC cap with wires coming out of it—and loosen it by hand so air can flow inside the system. Once this is done, water should drain out from each zone of the system’s mainline.
  • If your sprinkler system uses manual drain valves, locate the valve at the lowest point on your system’s mainline. Wear protective goggles for this, because the water can be under pressure and it’s possible to open valves before they depressurize. Next, turn off the the sprinkler system’s mainline shut-off valve. Then, open one of the control valves on the system. You may be able to do this from a controller, otherwise it’s a manual valve. Doing this will depressurize the sprinkler system mainline. Finally, slowly open the manual drain valve and allow it to drain fully. Follow this procedure for each manual drain valve on your system’s mainline. When all the water has drained, close each manual drain valve.

Step 3: Open all drain valves

Make sure there is no water left around any valves that may expand as temperatures drop after draining the mainline manually or automatically. You might have a “boiler drain valve” or a “stop and waste valve,” depending on your system, which will halt the local water supply and also permit draining that pipe. To drain the last of the water between the irrigation system and the backflow prevention device, find the valve’s drain cap and open the valve.

If you plan to hire professionals to perform a blow-out, proceed to Step 4; if you’re looking only to drain the pipes, you can proceed to Step 5.

Step 4: Consider hiring a pro (optional, but recommended)

Gravity will direct practically all of the water out after you’ve released the pressure in the mainline, assuming your sprinklers are reasonably fresh and placed appropriately with the irrigation pipes sloping downhill toward the valves (where water can escape at the lowest point in the system). But it’s difficult to be sure that none of it is still there, perhaps caught in a dip or curve in a pipe that has moved since installation. For this reason, authorities advise hiring a specialist to perform an additional safety measure that will let go of any final drops of water still trapped in the sprinkler system: blowing out the pipes using an air compressor.

You may have a similar machine to power your nail guns and other air tools. It may even be able to produce greater pressure than the suggested 50 pounds per square inch (PSI) required to blow out flexible polyethylene pipes from a sprinkler system or the 80 PSI required to blast out rigid PVC pipes. However, for two reasons, experts advise avoiding doing this following step on your own. Safety first: When using an air compressor, a variety of injuries, including those caused by flying debris and valve tops that explode, are possible. Second, compared to the unit used by professionals, the normal home air compressor may produce nearly the same force but less volume (a 10 cubic-feet-per-minute compressor). They can operate faster and more thoroughly than homeowners’ equipment, which might take much longer and possibly leave water behind—a risk that no one should take.

The pros should also close the main shut-off valves after blowing out your sprinkler system zone by zone using their air compressor connected to the hose coming from the water main supply. Additionally, they will remove any water that accumulated around your backflow preventer, which prevents system backflow and protects it from damage.

Step 5: Insulate any system components located above ground

It is recommended to insulate the exposed components of your system, including any pipes, backflow preventers, and main shut-off valves, if they are at all aboveground. Foam insulation tape, foam pipe covers, and other winterizing protection should be available at your neighborhood hardware store. Cover exposed pipes and other system components as directed on the foam insulation product packaging to prevent freezing or cracking. Take care not to obstruct drainage ports or valves.

Step 6: Program the system not to run during the winter season

Turn off your system for the season if it is timed. (Remember to update the software in the spring!) If you have a “rain mode,” it’s also possible that when it rains during the regular season, the sprinklers turn off without the timer being turned off. For the winter, you can use rain mode to turn off the system’s irrigation altogether. By doing this, you may prevent the system from turning off and losing the programmed settings, saving yourself the headache of having to reprogram it in the spring. Since the sensor consumes so little energy, leaving it on throughout the winter won’t increase your energy costs. Simply switch off the rain mode in the spring, and irrigation will restart automatically.

Bottom Line

With the help of the information above, you can almost complete the required winterization on your own once you know what kind of system you have, however you should always keep your owner’s handbook close at hand for reference.

We are strongly advised not to skip Step 4, which is the professional section of the procedure. This extra step, which typically costs approximately $85, could end up saving you hundreds in replacement or sprinkler system repairs.

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