Preparing an Irrigation System for a Cold Winter

The coming of winter can be a stressful time for some. If, for example, you invest a lot of time in your lawn and garden, then lawn and garden care experts suggest that you take certain steps to prepare your garden and lawn for the winter. Homeowners are also advised how to winterize their lawnmower so it too is not damaged during the cold months.

While you go about preparing your lawn and garden as well as the rest of your home for the winter, are you neglecting your lawn’s irrigation system?

(Courtesy: Green Again Irrigation at

(Courtesy: Green Again Irrigation at

If not properly winterized, the irrigation system can suffer some catastrophic damage. For example, ice resulting from frozen water can expand and burst the pipes of the irrigation system.

So it is more than imperative that you include your irrigation system in your plans to prepare for the winter.

If you live in a warm climate, then simply shutting off the system’s water supply and letting the water in the pipes drain out will probably suffice. However, if you live in a region of the country that experiences harsh winters, then you need to consider the so-called “blow out” approach to clear the irrigation system of water that could freeze.

The so-called “blow out” method refers to the use of an air compressor to rid the pipes of water. Although it may sound like an extreme action, if done properly, it is very easy to perform. Still, if you feel uncomfortable about trying it, then it is suggested that you seek the assistance of a professional irrigation contractor to perform the task.

If you are interested in tackling the chore, then you will need a few things to protect yourself as well as perform the activity. They include:

· Safety glasses
· Air compressor
· A key to turn off underground valves
· Coupler to connect the air compressor to the mainline of the irrigation system.

Prior to starting the project you will need to locate the main shutoff valve, the drain valves and the tie in for the air compressor.

You also need to rent or purchase the proper type of air compressor to perform the task. For example, you will need a machine that can push a large volume of air through the pipes at low pressure of between 30 and 60 psi. Cubic Foot per Minute (CFM) is the measurement for air volume. Most companies that would handle this task would use a tow-behind compressor with a CFM rating of 125 to 185. You can find one at most home equipment rental stores.

Experts suggest that an air compressor with a minimum of 60 psi at 15 CFM will suffice.

The psi you intend to push through the pipes of the irrigation system should not exceed the operating pressure of that system. Check the “as built” drawing of the system for the GPM and operating pressure is was designed for.

Now it’s time to pull out a calculator. To determine the ideal size of the right compressor to do the job, you need to compute this equation:

GPM of the irrigation zone divided by 7.5 gallons = CFM needed

The compressor you use should feature a pressure regulator. This will assist you in winterizing the irrigation system with less chance of damage of its components. Make sure that the air pressure does not rise more than 80 psi for irrigation systems that use PVC pipes or 50 psi for systems that use polyethylene pipes.

When you’re ready hook the air compressor to the irrigation system. Use a quick coupler to attach the machine to the mainline, hose bib or other type of connection. This is commonly located beyond the backflow preventer. Be sure that you don’t connect the compressor through the backflow preventer.

Slowly apply air into the mainline without blowing sprinkler heads or valves out of the ground.

Set all zones to run for two minutes from the control box of the system. Treat one zone at a time allowing the air to blow water out of the irrigation system. When the last two to three heads start blowing out mist, move to the next zone.

Blow the air through all zones at least twice to assure that most of the water is gone and shut off a zone once it is dry. The friction of the air blowing through a dry zone could damage parts.

Turn the system’s control box off or unplug it so that it can’t unintentionally open valves during the winter. This could damage the solenoids due to running them while dry.

After the entire irrigation system has been blown out, inspect the backflow preventer to ascertain if the water has drained. If not, open and close the valve of the preventer a few times. Leave the valves on the backflow preventer half open over the winter.

About Robert Janis

Written by Robert Janis for LawnEq - Your specialists for Lawn Mower Parts and Small Engine Parts. We offer genuine premium OEM parts for Land Pride, Toro and many more dependable manufacturers.

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