To manually drain the valve, first turn off the sprinkler system mainline shut-off valve (A) as shown in the accompanying diagram. Then open one of the sprinkler system control valves, either manually or electronically from the controller, to relieve pressure on the sprinkler system mainline. Slowly open the manual drain valve (B). Repeat this procedure for all manual drain valves on the sprinkler system mainline.

Contractors should note that draining valves using gravity or activating the valves manually does not remove water captured inside the valves. Valves must be disassembled to remove standing water (unless they are winterized using blown compressed air). Manual valves should be left in the open position throughout the winter to prevent re-pressurization.

Some sprinkler heads have both side and bottom pipe inlets. If the side inlets are used, install a drain valve on the bottom inlet to prevent the case from freezing. Sprinkler heads with built-in check valves to prevent low head drainage must be disassembled or blown out with air.

Irrigation valves should be disassembled and wiped dry to prevent residual moisture from freezing during very cold weather.
Photo courtesy of Rain Bird

Automatic Drain Valve Method

The automatic drain valve is a spring-loaded device installed on sprinkler heads or lateral pipes. The drain valve opens every time the system is shut off and drains all water from the pipe. When the system is pressurized, water presses against the sealing mechanism, shutting the valve and allowing water to flow through the pipe and to the sprinklers.

Automatic drains should be installed after or downstream of the sprinkler control valves at the low points in the sprinkler lines. Usually one or two drains per line are adequate. These drain valves simply screw on using male pipe threads. Teflon tape wrapped two or three times around the connection ensures a proper seal. A small dry well directly beneath the drain assists with drainage for poorly draining soil.

Because automatic drain valves remove water every time the system is shut off, no manual intervention is required for this stage of winterizing. Simply check for excessive puddling on the soil surface, which may indicate that one of the drains has become stuck open during sprinkler operation. As with the manual method, draining or activating remote control valves from the controller does not remove water captured inside the valves. Valves must be disassembled to remove standing water (unless you winterize using blown compressed air).

Water will flow out of each zone?EUR??,,????'?????<
Photo courtesy of Rain Bird

Compressed Air Blowout Method

The compressed air blowout method uses compressed air to clear water from the mainline pipe, sprinkler control valves, lateral pipes and sprinkler heads. Contractors should be advised to use extreme care when using this method to winterize the irrigation system. Excessive pressure (above 50 lbs. per square inch) can damage valves or sprinkler pipes or can generate flying debris, causing physical injury to the operator. Contractors should never stand over irrigation pipes, sprinklers or valves during this process.

To obtain proper air volume, contractors should use a compressor capable of providing 10 to 25 cubic feet per minute (CFM) of air volume. It is important to rent or buy the right air compressor for the job as some small shop compressors of two hp may not be adequate. However, air pressure must not exceed 50 psi during the blowout procedure. Using a pressure-regulating valve to avoid over-pressurization, contractors should keep air volume high and air pressure low to minimize the potential for damage.

Contractors should not try to use an air compressor with high pressure (120 psi) and low volume to evacuate water from the system. Even if the system can withstand 120 psi of water pressure, similar air pressure will damage the system. The viscosity of air is much lower than water, generating much higher stresses. Also, don?EUR??,,????'?????<

To hook up the air hose, the sprinkler system mainline should offer a separate quick-connect fitting, manual gate valve, plugged ?EUR??,,????'?????<

Blowing out a system using a timer is safer than activating the valves manually. If the system has a timer, follow those guidelines described first.

To manually drain the valve, first turn off the sprinkler system mainline shut-off valve (A). Then open one of the sprinkler system control valves, either manually or electronically using the controller, to relieve pressure on the sprinkler system mainline. Slowly open the manual drain valve (B). Repeat this procedure for all manual drain valves on the sprinkler system mainline.
Illustration courtesy of Rain Bird

Using the Controller

To winterize the irrigation system using the controller, close the mainline sprinkler shut-off valve (A). Relieve the water pressure on the mainline by activating a circuit or zone from the controller. Activate the circuit that is farthest from the air connection before letting air into the piping. Always keep a sprinkler zone control valve open from start-up to compressor shutdown. Attach the compressor hose to the blow-out adapter???????(R)???????+???????(R)???????(C). Set the pressure-regulating valve on the compressor to 50 psi and turn on the compressor. Gradually increase the flow of air until all the sprinkler heads pop up. The amount of flow or volume required will depend on the length of pipe and number of heads but contractors should not blow any circuit more than two minutes at a time. Sustained heat from the compressed air may damage pipe and sprinkler drive mechanisms that use water for lubrication and cooling. Switch to another station or zone by advancing the controller to the next circuit. Do not turn the controller off at any time during this operation unless the compressor is first shut off.

To ensure that lines adequately drain, repeat the cycle two or more times, activating each zone from the controller until nothing more than a fine mist appears from the heads. After blowing out all the zones, leave one zone on while shutting down the compressor. You may then unhook the compressor from the mainline and turn off the controller.

Manual Valve Activation ?EUR??,,????'?????<

To activate valves manually for the blowout, close main sprinkler shutoff valve (A). Relieve the water pressure on the mainline by slowly opening the manual shut-off handle on one of your irrigation zone control valves. Attach the compressor hose to the blow-out adapter???????(R)???????+???????(R)???????(C) and set the pressure-regulating valve on the compressor to 50 psi. Manually open the irrigation station you want to blow out before turning on the compressor. Gradually increase the flow of air from the compressor flow valve ?EUR??,,????'?????<

The flow or volume required will depend on the length of the pipe and the number of heads. Do not blow any circuit more than two minutes at a time as sustained heat from the compressed air may damage pipe and other components. After two minutes, turn the compressor off and allow the air to completely purge from the compressor tank and sprinkler system.

Turn on the next irrigation control valve you wish to winterize before turning off the irrigation control valve that was previously blown out. Repeat these steps until each zone has been blown out at least twice and only a fine mist is blowing from each station. After turning the compressor off, allow any air in the storage tank or irrigation components to disperse before approaching the air hose or valves. Unhook the compressor from the adapter to the sprinkler mainline.

Taking the time to winterize all parts of a sprinkler system will not only protect it this winter, but will also extend the life of the irrigation components so they can serve for years to come.

Rod Waller is a Contractor Account Manager for Rain Bird Corporation in Florida.