How to Blow Out Sprinklers and Winterize Your Watering System

Winterize Sprinkler System

It’s a nightmare situation for water sprinkler owners come wintertime: Busted pipes! Broken seals! Ruined valves! What do you think could be the culprit?

It may be frozen water in your sprinkler system. And we all know what a pain it is to fix such a problem. Not only is it costly, but it will also require extensive digging. Fortunately, there is a quick solution to prevent this doomsday scenario: sprinkler winterization.

This process is a crucial step to take when the chilly weather starts to come in. Draining water from your entire system is necessary to prevent any damage. Luckily for you, this is relatively easy to do. Chances are you already have the tools needed to do this sprinkler blowout yourself.

Winterizing Your Sprinkler System

Just follow these few simple steps to winterize your sprinkler system:

1. Cut off water to your sprinkler system

As with any maintenance work, you need to shut off water into your sprinkler system. Most have an emergency shut off valve to do this. This is usually buried below ground in a valve box and may require an extended key to access it.

If your sprinkler system comes with a pump, you need to tackle this as well. Detach this from the system and completely drain any water inside. If your pump is permanently mounted in, you can insulate it instead to prevent it from freezing over.

2. Purge the backflow

If your water system has a backflow installed, you need to purge this first. These devices can be one of two kinds: Pressure Vacuum Breaker (PVB) or Atmospheric Vacuum Breaker (AVB).

You do not need to complete any additional steps with an AVB device. PVBs, however, are susceptible to warping and heat damage from compressed air. After you have purged your system, recheck the PVBs for any damage. Leave them in a slightly open position to prevent any moisture from building up.

3. Drain the water out of the system

This step is the main star of the show, where you remove all the water from your sprinkler system. The best way of doing this is by using an air compressor to push out all that water.

To figure out the correct volume of compressed air to use, you need to know the gallons per minute (GPM) rating of your sprinkler system. You can glean this information from the design plans of your system. If this is not available, you can make a rough estimate. Get the GPM rating of each sprinkler head based on the manufacturer’s specs. Multiply that for each head in the zone to get that zone’s GPM rating.

Once you have the GPM rating, you can use a simple formula to figure out the required volume of your compressor. Divide the GPM by 7.5 to get the necessary amount of air in cubic feet per minute (CFM). Use this information to figure out the correct size air compressor to use.

To do the actual purge, attach the compressor to the backflow device. Note that this needs to have a blowout valve installed, or else it will not work. Next, turn on all the nozzles in the affected zone. Finally, turn on the compressor at the correct PSI setting, and then let it rip! Continue running it until no noticeable moisture is coming out of the nozzles.

We recommend doing this in two short cycles instead of a long one. This step ensures the maximum amount of purging. And whatever you do, don’t purge your system twice. It will introduce unnecessary heat into your pipes and valves!

If you happen to have a bigger sized air compressor, you can still use this as long as you have a regulator installed. Not doing so will lead to too much blowout, damaging your valves and warping your pipes. Smaller air compressors are safer but will take a longer time to purge. It can also lead to overheating the compressor itself.

Keep in mind that you need to reach a certain point for both air and water volume to purge your system efficiently. This is usually 80 PSI max for rigid PVC pipes, and 50 PSI for polyethylene. Please know what pipe you’re using to prevent too much pressure bursting your pipes!

Don’t forget to work safely. Wear protective goggles in case loose fittings unexpectedly fly to your face.

4. Program your controller

After purging, you need to program your controller to run a few minimal cycles every week. This process gives off a small amount of heat that prevents any moisture build-up inside the pipes. This is also a way to keep the plungers and valves from freezing and getting stuck. You also need to turn your backflow device’s valves partially open during this time.

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