Irrigation Solutions
Serving central Ohio since 2001
Every year, before the first freeze, the ritual of irrigation "blow out" becomes the priority for all irrigation systems in regions located where the frost level extends below the depth of installed piping.
Even if you have drained the water out of your irrigation system, some water remains and can freeze, expand, and crack PVC piping. Polyethylene pipe (flexible, black pipe) is used in many freezing climates. Although polyethylene pipe is more flexible and can expand under pressure, water left inside can freeze and rupture the pipe walls. Freezing water in the backflow assembly will damage the internal components and can crack the brass body.
To minimize the risk of freeze damage, you'll need to winterize your irrigation system. In areas where winterization is mandatory, irrigation systems are installed using one of three types of water removal: manual drain, auto drain, or blowout. If you don't know your system type, it is best to use the blowout method.
Due to potential dangers involved with winterization, it is best to call a professional
The blow out method utilizes an air compressor with a Cubic Foot per Minute (CFM) rating of 80-100 for any mainline of 2" or less. These types of compressors can be rented at your local equipment rental yard. Caution: a small shop compressor (1-3 HP) will not have enough "free" air to properly winterize the system. Do not attempt to fully charge the holding tank then release the highly-pressurized air flow into the mainline to compensate for the compressor's lack of CFM.
To start the blow out, shut off the irrigation water supply and, with the compressor valve in the closed position, attach the air compressor hose to the fitting. Activate the station on the controller that is the zone or sprinklers highest in elevation and the furthest from the compressor. Close the backflow isolation valves. Then slowly open the valve on the compressor; this should gradually introduce air into the irrigation system. The blow out pressure should remain below the maximum operating pressure specification of the lowest pressure rated component on that zone and should NEVER exceed 80 PSI. Each station/zone should be activated until no water can be seen exiting the heads; this should take approximately two minutes or more per station/zone.
Compressed air moving through dry pipes can cause friction, which will create heat and could cause damage. Never run the compressor without at least one irrigation control valve open. Once the water has been removed from the irrigation system, disconnect the air compressor and release any air pressure that may be present. If your backflow device (the most common backflow installed is called a Pressure Vacuum Breaker) has ball valves, open and close the isolation valves on the backflow device numerous times to ensure that any trapped water has escaped from the upper areas. Leave the isolation valves open at a 45° angle (approximately 1/2 open) and open the test cocks.