Freezing nighttime temperatures can damage exposed water lines and automatic irrigation valves that control the water to your sprinklers and drip emitters.
Plumbing exposed to the open air is most vulnerable to freeze damage—usually irrigation valves or where the water service line enters a building. If water freezes inside exposed water lines and valves, the force of expansion can be enough to crack pipes or break joints.
If your pipes have frozen
DO wrap the house valve in a towel and slowly pour warm (not boiling) water over it. You'll find warm water in the bottom of your water heater.
DON'T use a torch, heater or any open flame.
Prevent pipe freezing
DON’T try to prevent freezing by opening a faucet to keep the water moving in the pipes. This is an unnecessary waste of water.
DO wrap exposed plumbing parts with insulating material from your hardware or home improvement store. Old towels will work in a pinch. It's also a good idea to insulate faucets and pipes in unheated areas (garages, crawl spaces).
DO protect automatic irrigation valves from freeze damage by shutting off the valve in the water line that feeds those valves. Then, use your irrigation timer to turn on each valve for a minute to drain water from the valves and pipes.
DO turn your irrigation system off for the winter and let winter rains and cooler weather care for your plants.
DO open the shut-off valve(s) and test your irrigation system before starting it back up in the spring.