Winterizing your customer’s irrigation system

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Updated Oct 7, 2021
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For those landscapers in regions that will soon begin experiencing freezing temperatures, it’s important to begin the process of winterizing your customers’ irrigation systems.

The main objective for winterizing irrigation systems is to remove all water from the system. Irrigation systems that are not winterized properly can often display signs of damage later on in the spring, and when water is left behind in the pipes during winter, it will expand and freeze. This can cause fittings or pipes to burst.

Take a look at what you should keep in mind when beginning to winterize your customers’ irrigation systems.

When to winterize

One of the most common questions when it comes to winterizing irrigation systems is when exactly to start the process.

Choosing to winterize an irrigation system really depends on what part of the country you live in and how the irrigation system is used. Generally, Toro recommends beginning winterizing when you’ve experienced three or more days at three degrees below freezing (32˚F / 0˚C). This is when water will begin to freeze deeper in the ground where the laterals are typically buried. If it looks like freezing temperatures for your area will be extended, go ahead and evacuate the system.

Which method to use?

Also called decommissioning, winterizing an irrigation system can vary depending on your regions, but overall the principles are similar.

Winterizing irrigation systems is a straightforward process, and if at all possible, it should be done before the first frost arrives. Winterizing is usually accomplished by one of three methods: manually draining, automatically draining or the blow-out method. The blow-out method is considered the most effective method of ensuring there’s no water left in the pipes.

According to Toro, there are a few essential steps to take when winterizing an irrigation system. Be sure that all water and electricity are turned off so there is no source of pressure in the system. If there’s a pump or other electrical component, turning off the electricity will keep it from getting accidentally switched on during the off-season.

The Michigan State University Extension also recommends keeping an eye on trickle and drip lines and tape. While these are designed to be self-draining, manifolds and supply systems still need close attention to make sure no water pockets are left over to freeze. Damage done by rodents in the winter can also turn once-usable trickle lines into a mess quickly, and lines that are going to be moved the next year should be stored.

Next, be sure to drain all of the water and to pump down or drain underground pipelines. Many of the underground pipelines are far enough down that they don’t get much freeze damage, however, they do require pumping or draining enough water from them to empty the upper portion of Z-pipe risers and pump manifolds.

This can be accomplished by purging the system with air or by modifying a fertilizer pump to pump the system at its lowest outlet or inlet points. All pipe inlets and outlets should be capped to prevent animals from getting in, as well. The systems can be emptied either by gravity or by using a pressure source such as air.

Last, go ahead and create a winter work list for each of your systems. Before you forget, make a list of the repairs and improvements that are needed for each system.

How long does it take?

The length of time dedicated to this task will depend on the size of your customer’s property, but typically, Toro says it can take several hours per zone to complete all the steps and check the heads for larger areas.

Toro recommends keeping in mind that the time will increases at a 4-to-1 ratio when you scale up the size of a project, which means the pipes and heads will be twice as big.

Keep in mind

Always remember that you’ll need to wear ANSI-approved eye protection when winterizing an irrigation system because compressed air can cause serious eye injuries. Be sure to avoid standing over any of the irrigation components during the blow-out process.

Never exceed 80 pounds per square inch (psi) when using an air compressor in the winterizing process, and avoid using compressed air on the backflow device, as the rubber seals on a pressure vacuum breaker can melt from the heat of the air.

Once the pipes have been blown out, be sure to avoid exposing them to more compressed air, as this can cause friction and heat that will damage the system. Unless at least one irrigation control valve is open, do not run the compressor.

When choosing what kind of air compressor to use, it’s important to be sure of what size you’ll need. Smaller units might struggle to provide the proper amount of pressure and volume that you’ll need to completely purge the system, while a larger one could run the risk of purging just a little too quickly and damage the system.

To calculate the right size, simply know the gallons per minute (GPM) that flows through each zone of the system. Divide the GPM by 7.5 to determine the cubic feet per minute (CFM).

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