Winterizing Your Irrigation System
Each winter, in much of the world, irrigation systems must be "put to bed" for the season. Because of the inevitable arrival of freezing weather from the north (global-warming not withstanding) they must be completely drained and dried to prevent damage to the system components caused by water freezing inside the pipes, sprinklers and valves. Serious damage and/or personal injury could result if improper winterization methods are used.

There are a two ways to get your system ready for winter: pay someone to do it for you, or, do it yourself. The easiest option is to just hire an irrigation contractor to come to your home and do the job. Depending on the size of your system it will cost you between $50 and $150 a year to have a contractor winterize your system. The other way, the DIY way, will save you those dollars. After the first time, it should not take you more than one hour to put your irrigation system to bed for the cold months. All that money you save you can put to other uses - like maybe a new snow thrower to ensure that you don't end up hibernating all winter like your irrigation system.

The Contractor Approach
When contractors winterize a system, if it doesn't already exist, they will install a drain valve, or other fitting for attaching a compressed air hose, downstream of the anti-siphon device, outside of the house. The air is used to blow all water out of the system.

After shutting off the water to the system, the technician will attach the compressed air hose to the blowout connection, and one zone at a time, blow out all the water. After the system is blown out, all that is left to do is drain the line between the backflow prevention devise and the shut off valve.

The DIY Way
If you want to do the job yourself, and put the money you will save toward your new snow blower, or gas for your sled, or that trip to Disney World, there are a couple different tacks you can take: drain the system using drain valves, or blow out the system the same way a contractor might. If you (or your neighbor) don't own a good-sized compressor then the easiest way is to just drain the system.

Drain valves are usually installed when the system is installed. Adding them later is time consuming, but not out of the question, considering the money you could save by doing so. They will need to be placed at the low point of each zone. Use at least one drain per zone. In soils that drain poorly, you may need to dig a drywell (a 6"-8" deep hole, with a few inches of gravel in the bottom) below each drain valve to ensure that no water collects there. There are two types of drain valves to use, manual or automatic.

Manual Drain Valves
If your system uses manual drain valves, the first thing to do is to shut off the main irrigation water supply valve. It should be located near your water meter, at a tee connection. If applicable, turn off the power to your well pump and drain those lines too.

Next, open all the drain valves downstream of the zone valves to allow drainage of the lines. Leave them open for a few hours or even a couple days to allow all the water to escape.

Finally, open the drain valves upstream of your zone valves to drain the main irrigation supply line. Even if this line is in your basement, it should be drained since it runs through the foundation wall of your home and is exposed to outside temperatures.

Automatic Drain Valves
If your system is installed with automatic drain valves, the lines downstream of the automatic zone valves will drain whenever there is no system pressure. But it is a good idea, to check that the drains are working. Do this by watching each zones operation. Systems using automatic zones require a few seconds to "charge" before the sprinklers operate. If a zone operates to quickly the drains may not be draining properly. If in doubt, remove a sprinkler to check for standing water in the line.

Next, open any drain valves upstream of the automatic valves to allow drainage of the plumbing that runs between the main shutoff and the valve manifolds.

Zone Valves
If you want to be sure your zone valves are dry and protected, the best thing to do is to remove them for the winter, and then reinstall them in the spring. Depending on the size of the system this could take a few hours to accomplish.

The "BIY" Way
The best way, is the BIY way. If you own a 25 CFM or larger compressor, with a pressure regulator adjustable to 40 PSI or less, you can winterize system by "blowing-it-yourself." This is the same procedure a contractor would use.

CAUTION
Do not exceed 40 PSI (2.8 kg/cm2) of air pressure. Exceeding 40 PSI can result in severe equipment damage.

1. Shut off the main water supply valve.
2. Connect the air compressor to a fitting downstream of the main water supply valve.
3. With the air pressure applied, activate each automatic valve manually from the controller. Let each zone valve remain open until all water has been expelled from that zone. DO NOT blow the zone any longer than needed.
4. After all the valves and zones have been blown out, disconnect the air hose.
5. Finally, open any drains that are installed between the main shut off and the valve manifolds. To use this method you will have to install a suitable connection for the air hose downstream of the anti-siphon device.

See You in the Spring!
The key to winterizing your system is to be patient and thorough in your approach. It is amazing where water can hide in a system, and just doing things like leaving your drain valves open for a few days in order to let them dry out completely can make all the difference next spring when you recharge your system. So, don't be in a hurry now, and you will have a much more pleasant start-up in the spring.