How to Winterize a Sprinkler System
The process on how to winterize sprinkler system always takes top priority just before the onset of the first freeze every year. This is particularly true in regions where the frost levels extend below the installed piping depth.
Some water may remain after draining the sprinkler system. IF PVC piping is installed, it can lead to freezing, expanding, and cracking on the rigid white pipe. Even the black Polyethylene pipe (commonly used in most freezing climates) that is designed to be more flexible and to expand under pressure can be damaged. This is because the remaining water inside can freeze and may crack the pipe walls. Frozen water in the backflow assembly can likewise affect the internal parts and can rupture the brass body.
Winterizing the sprinkler system is done to mitigate the risks of freeze damage. In jurisdictions where winterization is required, irrigation or sprinkler systems are installed using any of the three water removal types – automatic drain, manual drain, or blow-out. If you are not aware of the type of system you have, the blow-out method is recommended.
The Automatic Drain Method
This method is used for systems where automatic drain valves are found at the low and end points of the sprinkler system. if the pressure on the piping is under 10 PSI, the valves will open automatically and drain the water inside. To have these activated, cut the sprinkler system water supply off and trigger a station to ease system pressure. Usually, the shut off is in the basement and may either be a ball, gate/globe, or stop and waste valve.
Once the main line is drained, open the drain cap (if the stop and waste valve is installed) or the boiler drain valve (for other types of valve) and drain the water that is remaining in between the backflow device and the sprinkler system shut off valve. Open the backflow device’s test cocks. If your system is equipped with check valves, pull the sprinklers up so water from the bottom can be drained. Some water may remain on the piping, backflow, and sprinklers, depending on where the drain valves are located.
Some regions use a combination of the auto drain (on lateral lines – the pipe between the sprinklers and valves) and manual drain (on the main line – the pipe between the valves and the sprinkler shut off) methods to winterize sprinkler system.
The Manual Drain Method
This method is used when manual valves are situated at the low and end points of the piping. To drain, just cut off the water supply and open all of the system’s manual drain valves.
Once the main line is drained, open the stop and waste valve’s drain cap or the boiler drain valve, whichever is applicable to your system, and drain the leftover water nestled in between the backflow device and the water shut off valve. Then, open the test cocks installed on the system’s backflow device.
If your sprinklers come with check valves, pull the sprinklers up to let the water from the bottom of the sprinkler’s body drain out. Depending on where the drain valves are located, some water may remain in the sprinklers, piping, and backflow. Make sure that all manual drain valves are closed once all the water has been led out.
The Blow Out Method
When blowing out a sprinkler system with compressed air, extreme caution must be observed. Thus, safety eye protection gear, ideally ANSI-approved, must be worn. This is because compressed air can cause serious physical injuries including eye injuries, due to flying debris.
Always protect yourself and never stand over any of the system’s components (sprinklers, valves, and pipes) when performing air blow out. Otherwise, injuries may be incurred. If you think you cannot carry out this method on your own, you may have a licensed contractor do the job for you.
The blowout method uses an air compressor with a rating of 80 to 100 CFM (cubic foot/minute) for main lines measuring 2 inches or less.
Compressors may be leased from a nearby equipment rental shop. Just a bit of caution, though: a small compressor with 1-3HP may not have sufficient free air to winterize sprinkler system properly. Thus, never try to charge the holding tank to full capacity and then release the high pressure air flow into the main line to make up for the compressor’s CFM inadequacy.
The compressor is hooked to the main line through a hose bib, a quick coupler, or some other connection types located somewhere near the backflow device. To begin the blow out process, cut off the water supply. Attach the hose of the air compressor to the fitting, while making sure that the compressor valve is closed. Activate the controller station that is typically the sprinklers or zone with the highest rating and found farthest from the compressor.
Close the isolation valves on the backflow device, and then slowly open the compressor valve. This process will slowly introduce air into the sprinkler system. Make sure that the blow out pressure stays under the maximum recommended operating pressure of the lowest rated component in the zone; and never allow it to go over 80 PSI.
Each station or zone must be activated commencing from the one farthest from the compressor. Slowly work your way up to the nearest station or zone. Activate each one until there is no more water coming out from the heads. Using 2 to 3 short cycles for every zone/station is more preferable than having a single long cycle.
When the zone or station is dry, stop blowing air into the pipe because compressed air passing through dry pipes may trigger friction that in turn will induce heat that may cause rupture. Likewise, keep in mind that the compressor must not be put in operation unless at least one sprinkler control valve is open.
Additional Procedures to Winterize Sprinkler System
After removing water from the sprinkler system, detach the compressor and release whatever air pressure may be left. If the backflow device installed in your system comes with ball valves, the isolation valves on the backflow must be opened and closed several times to make sure that any water trapped inside has been drained through the upper areas. The isolation valves must be left half-open or at a 45 degree angle. Open the test cocks as well.