University of Nevada Cooperative Extension
Now that night temperatures are dipping below freezing, it’s time to think about turning off your irrigation system.
Shorter days, cooler temperatures and plant dormancy, all signal decreased needs for water. To avoid damage from freezing, shut off your system before cold temperatures arrive. Watch the weather and the long-term forecasts to know when the time is right to shut down your irrigation system. Most years, you’ll want to turn it off by Halloween.
Before you do, soak your trees and shrubs to a depth of 18 inches to make sure the soil is moist. Irrigate to the drip line of the plants — the outer tips of the branches — using soaker hoses or sprinklers. Most drip systems, unless they are sprayers, don’t provide sufficiently uniform water coverage to do the job.
To determine if you’ve watered enough, stick a piece of rebar, a long screwdriver, or another indicator into the soil. If it pushes in readily to the 18-inch depth, you’ve watered enough. You can also dig a hole to the 18-inch depth to check soil moisture, but be sure to avoid damaging the roots. Note about how long you watered, and you’ll be ahead of the game next year.
To avoid damage to irrigation systems, take a few steps to prepare them for winter. If you don’t, you can expect to spend time next spring digging up your water lines to repair winter freeze damage. You can hire a professional lawn service to do the job, or do it yourself.
To winterize your irrigation system, start by turning off the controller, if you have one. Check the owner’s manual to figure out how to do this. Then, shut off the water to the irrigation system at the main valve.
Next, drain any above ground irrigation components that hold water. Blow out the pipes in your sprinkler system, keeping the pressure under 50 pounds per square inch (psi). Experts advise blowing out each valve in the system, and then repeating the process a second time. Be careful and wear safety goggles. If this sounds too complicated, or you don’t have an air compressor, consider hiring a contractor to do this part.
Don’t forget to drain your drip system. Since drip lines are usually on the ground surface or under mulch, they’re susceptible to freezing.
With the water turned off, undo the end caps and let the system drain. If you want to use a compressor, keep the pressure under 30 psi to avoid damaging system components. Don’t forget to put the end caps back on to keep water and debris from clogging up the system. You don’t need to move the tubing or emitters once emptied, but timers should be stored at above-freezing temperatures.
Even with your system shut down for winter, some plants still need water. Trees should also be watered if it’s been three to four weeks without significant precipitation such as an inch or so of water. Be sure to water the root ball of newly planted trees regularly through the winter and early spring.
Roses also appreciate water during the winter. Use a watering can to apply a few cups of water at least once a month, but don’t prune them now. Wait until spring.
Most lawns will do just fine without winter irrigation. The exceptions are newly seeded or sodded lawns that have not yet developed robust root systems. They’ll also need water if it’s been dry for three to four weeks, as long as the soil is not frozen.
If you don’t want to fire up your irrigation system, use a hose and sprinkler. A little winter care will yield healthy plants in the spring.
Susan Donaldson is water quality and weed specialist for the western area of University of Nevada Cooperative Extension.