How to Winterize a Sprinkler System Mid-Winter How to Winterize a Sprinkler System Mid-Winter

What You'll Need
Hot air compressor

If you live in a mild climate, it's not a problem to winterize a sprinkler system mid-winter. If, however, you live in a cold-weather part of the country and you did not take the steps to winterize the sprinkler system before winter, you may have some problems. These problems will be magnified if you have already experienced the first bout of freezing temperatures for the winter. The danger in not winterizing your sprinkler system in a cold area of the country is the risk that any water in the system will freeze and possible cause the pipes to burst.

The easiest and most efficient way to winterize your sprinkler system is to use an air compressor. You can rent or purchase a compressor from a local hardware store. The compressor will need cubic feet per minute (CFM), a rating of 80 to 100 for any mainline with a 2-inch or less diameter. A compressor that's too small will not produce enough air to do the job. Once you have the compressor, you can follow the steps below to make sure you winterize your system correctly and protect the sprinkler system during the winter season.

Step 1 - Shutting Off the Water Supply

Water supply lines.

The first thing you must do is turn off the water supply at the main water valve to ensure no more water enters the system. The shut-off valve is usually located in an area that is not prone to freeze over, such as inside the home, garage, or utility closet. Once the main water supply is cut off, all you have to do is drain the water that is currently in the system.

Step 2 - Connecting the Air Compressor

Hook the compressor up to the mainline with an adaptor, which will be determined by the connection located past the backflow device. Keep the compressor valve in the closed position while you attach the hose to the fitting. The backflow preventer valves should be closed also. Make sure you do not blow compressed air through the backflow device.

Step 3 - Activate the Farthest Station

The farthest station should be activated first. The station will be the one for the sprinklers at the highest elevation, or on the controller that is in the zone farthest away from the compressor.

Step 4 - Filling System With Compressed Air

An air compressor.

Close the backflow isolation valves and then open the compressor valve slowly to allow air to fill the sprinkler system. The blow-out pressure should never exceed 80 PSI for PVC pipe systems or 50 PSI for flexible black polyethylene pipe systems. The operating pressure should also stay below the max operating pressure of the lowest pressure rated component in your sprinkler system

Step 5 - Activate Rest of Stations

Start with the furthest stations from the compressor first and work your way throughout the sprinkler system, activating the remaining stations slowly at each station or zone. Activate each station until no water is seen draining from your sprinkler heads. This usually takes about two minutes per station, maybe longer.

Try doing two to three cycles per station instead of doing one long cycle. If you think it'ss taking too long to drain water from each station, then deactivate the station early and repeat the process up to three times.

Once a station is dry, stop blowing air through it immediately! Continuing to blow compressed air through dry pipes can create heat and friction, which will damage the pipe. Always have at least one station valve open when running the compressor. Be sure to only run compressed air through one section or zone at a time because the excess velocity of the air can add heat and friction to the fitting and pipe which will cause them to melt.

Step 6 - Turn off the Compressor

Once all systems have been drained and are dry, disconnect the air compressor from the sprinkler system. Any delay may cause damage to the pipes. Once the compressor is off and disconnected, release any excess air pressure by opening the valves on the sprinkler system

Step 7 - Remove Excess Water From the System

If your sprinkler system has ball valves on the backflow device, then open and close the isolation valves on the device a few times, which will allow any water that may be trapped to escape. Keep these isolation valves open at a 45 degree angle and open the test cocks on the sprinkler system.

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