Keep Freeze Damage From Putting a Chill in Irrigation Systems

by Lynda Wightman - member of the NIAAA Sports Turf Advisory Committee

Every year, it's a ritual. From Maine to Minnesota to Montana - and anywhere the frost level could extend below the depth of installed pipe - getting an irrigation system ready for the change of seasons is annual event.

Coaches and sports turf managers need to be aware that over the years, the effects of repeated water expansion inside pipes can weaken those pipes and lead to fractures. Plus, if the fittings and the pipe do not expand and contract at the same rate during seasonal temperature changes, the matter of material stress will be called into question.

Of course, if your system contains PVC pipe, there is no question. Because, when it's more than half full of water and frozen, PVC pipe will crack - most often from fitting to fitting (i.e., along the length of the pipe).
You need to "winterize" your system to protect it. The only question is: "how?"

"Blowing Out" a System With an Air Compressor.
Unless your system has manual or automatic drains, you will need to "blow out" water in the system with a portable air compressor in order to winterize. And doing it all is rather easy.

After turning off the water, connect the compressor (100 CFM for pipe with 2" diameter or less, 250 CFM for pipe 4" or larger) to inject air into the system near the main shutoff. This could be a quick coupler valve and/ or a special valve installed for blowouts. Turn off the compressor and activate the zone of sprinklers at the highest elevation and furthest from the compressor before opening the valve on the compressor. Be careful to introduce air into the system gradually to avoid high-pressure surges. Then, slowly increase the air pressure to 50 psi to reduce the chance of water ram damaging the components. If the sprinkler heads do not pop up and seal, adjust the pressure upward until they do, but NEVER let the air pressure exceed 80 psi. It is not necessary and will have lasting harmful affects on the system components.

It usually takes about two minutes or more to evacuate each zone. Proceed in sequence through all the zones, eventually ending up at the part of the system closest to the compressor and at the lowest elevation.

Go twice through the entire system, using a short cycle on each pass rather than a single long one, as repeating the process completely removes water that has drained from one zone into another on the first cycle. It also helps reduce the amount of time compressed air is moving through dry pipes (such friction can cause heat damage).

Some Final Steps:
Got a controller? Be sure to leave your power on and the rain or station start switch in the off position to prevent condensation inside the controller enclosure. Have a backflow device with ball valves? After shutting off the water supply and draining the system, remove any water trapped in the valve bodies by opening and closing them several times with the lever handle. Then, leave the handle at a 45-degree angle, so the valve is partially open. Remove or wrap backflow device if necessary. Preparing a hydraulic control system? Close and disconnect the potable water supply line to the signal control tubing and drain the tubing.

Use a submersible pump? Remove the pressure relief valve and then “blow out” the lines with compressor as mentioned above. Re-install the relief valve and drain the pump (plug and/ or other valve). Make sure you remove the suction lines and take time to inspect and repair if required. In all cases, follow the manufacturer’s procedures.

That's it. Whether your system is a football field Indianapolis, a soccer field in Rochester or on a multi-function field in Saskatoon, the same rules apply. To prevent freeze damage you have to winterize your pipes.

"BLOW-OUT" WINTERIZATION CHECKLIST
• Don't allow air pressure to exceed 80 psi (especially in systems designed to operate below this pressure level)
• Don't stand over component parts while the system is under air pressure
• Don't leave the compressor unattended
• Don't blow out the system through a pump (first blow out the system, then drain the pump)
• Don't leave manual drain valves open (water could enter the system during a winter thaw)