Winterizing your sprinkler system in late fall is a necessary maintenance task in climates where winter temperatures drop below freezing. By manually draining, automatic draining, or blowing out the sprinklers with an air compressor, you purge all the water from the system, protecting it from winter freeze damage.
Step-by-step instructions for winterizing a sprinkler system
It’s pretty straightforward to winterize your in-ground sprinkler system by manually draining the water or using an auto-drain valve system (if you have one). However, most sprinkler contractors recommend homeowners in freezing climates have their systems blown out for the best protection.
Caveat: Every system is slightly different, but the basic winterizing principles are the same: You want to shut off the water to the irrigation system, expel water from the pipes and sprinkler heads, and drain water from the backflow preventer. Then, shut down the controller for the winter.
Shut off the water
First, turn off the water supply at your main shutoff valve. Sometimes, the shutoff is in the basement, a crawl space, or a valve box close to the water meter or main water line.
For systems with backflow preventers, you need to shut them off, too. In most cases, two valves feed into the backflow device. Both need to be shut off.
Turn off the watering programs
After shutting off the water, turn off all scheduled programs on the controller, but don’t shut it off completely. You may need to use the panel to activate zones and drain water from the lines.
Drain the water
When winterizing, one of the most important things is to drain each of the system’s sections rather than just focusing on the sprinkler lines and heads.
Steve Voss of Voss Land & Tree says, “The most important section to protect during the winter months includes the manifold, which is the main component of a sprinkler system and controls the water supply to different watering zones. Needing to replace the manifold can be both expensive and challenging.”
Auto-drain method
Some systems have auto-drain valves that automatically drain water when the pressure drops below a specified PSI. This function drains the water out of lines and heads when the shutoff valve is opened but may not release water from the valves.
Pro tip: As every sprinkler system is slightly different, find and follow your manufacturer’s directions to open and drain the auto-drain valves.
Manual draining method
Manually draining your system is more involved than auto-draining, but it isn’t difficult.
- Locate the manual drain valves at the low points or ends of the lines. Open them one at a time to drain the water. Once fully drained, close each valve before moving to the next.
- If your system has a backflow preventer, open the drain value to 45 degrees. Turn the test cock screws on the backflow lines to 45 degrees using a flathead screwdriver or small coin to let them drain. Leave ball valves in the 45° position after draining to avoid splitting.
- Find the valve box for each zone in the lawn. Open the manual drain in the manifold and let it drain.
- If your system has zone valves without manual drains, activate each zone, one by one, via the controller to push out any remaining water.
- Open the faucet next to the backflow to drain any water still in the line.
- Go back to the main shutoff valve in the basement, crawl space, etc., and open the drain valve next to it. If the water is in a finished space, use a bucket to catch it.
Air blow-out method
Winterizing your system via air blowout can be done as a DIY project, but keep in mind two important things: this method can be dangerous, and the air compressor you have in the garage may not be equipped for the job.
- Always wear eye protection and be cautious when blowing the water from your sprinkler system.
- You’ll need a compressor with a 50-100 CFM (cubic feet per minute) rating and air pressure of 30 to 50 PSI for sprinkler systems with a mainline smaller than 2 inches.
Pro tip: If you’re unsure or uncomfortable performing these steps, consider hiring a professional irrigation specialist to winterize your system and take notes. Next year, you can do it yourself. The national average cost of professional sprinkler winterization is $90, with most sprinkler systems costing $60 to $120 to winterize.
- Open any drains on the lines in the basement or outside to drain trapped water.
- Close the valve to the backflow preventer so the compressed air will not travel to your backflow device.
- Remove the cap to the blowout line.
- Twist on your compressor adapter and connect the air hose.
- Using the controller, turn on the zone farthest away from the compressor. (You don’t want to deliver compressed air to a closed system.)
- Turn on the compressor. Run a 2 to 3-minute cycle using a pressure of around 30 psi for polyethylene pipes and 50 psi for PVC pipes. As a general recommendation, never allow the air pressure to exceed 50 PSI for poly pipes and 80 PSI for PVC.
- Continue this process, moving closer and closer to the compressor until all the zones are blown out.
- If water remains after three minutes, shut off the cycle and move on to the next zone. After you finish all zones, run another cycle through each one. Multiple 2 to 3-minute cycles are better than a single 5- to 6-minute cycle.
- Turn off the compressor. Disconnect the compressor and adapter from the blowout line.
- Replace the cap loosely to leave room for water to drip out.
- Turn ball valves to 45 degrees on either side of the backflow preventer to prevent splitting. Turn each of your test cock screws to 45 degrees.
Insulate above-ground components
Protect any exposed pipes, the main shut-off valve, and the backflow preventer with foam pipe insulation or covers, using insulated tape to secure them. Supplies are relatively inexpensive and should cost less than $25.
Turn off the controller
Once the water is removed and the above-ground components are insulated, access the controller and shut it off completely. You don’t need to unplug it, but make sure it’s turned off so the system doesn’t try to turn on and run.
Note: Most systems can be safely powered off without losing the programmed settings. When turned back on in the spring, they should resume working seamlessly.
FAQs about winterizing your sprinkler system
What happens if you don’t winterize a sprinkler system?
If you don’t winterize your system, any water left in the lines, valves, or heads can freeze and expand. Like a can of soda left in the freezer, as the water freezes, it expands and can cause components to crack, bend, or burst.
Freeze damage can lead to costly repairs, especially if your backflow preventer is damaged. Frozen water in sprinkler heads can expand and cause problems with the internal pieces, rendering the heads useful or ineffective.
When to winterize your sprinkler system?
The exact timing depends on your local climate. The goal is to keep sprinklers running until your grass quits growing but winterize the system before your area starts getting consistent hard freezes at night or consecutive days with below-freezing temperatures. Most systems are typically winterized between the beginning of October and Thanksgiving.
Some things to consider in regards to timing:
- Colder climates see seasonal frosts earlier, so systems should be winterized sooner than more temperate zones.
- Systems with above-ground components should be winterized earlier to avoid damage to exposed pipes or a backflow preventer.
- Systems with only underground components can wait longer because the soil helps insulate everything.
According to the pros at A+ Lawn & Landscaping, “The general rule to follow is to winterize your system at least a week before the first freeze is expected.”
Will a hard freeze damage my system if it hasn’t been winterized yet?
Thankfully, you don’t have to panic if an early-season freeze is forecasted to hit your area and you haven’t winterized your sprinklers yet. The season’s first freeze isn’t enough to damage the underground components because the soil acts as an insulator until the soil temps drop and the ground freezes.
It can damage exposed pipes or backflow devices, so cover above ground components with blankets or old towels until you can winterize the system.
Need professional help?
By the time October rolls around, many of us have a fall to-do list that feels like a mile long. Between clearing out the garden, mowing the lawn for the last time, and applying that fall fertilizer and pre-emergent, you may be running out of free time to get things done before the snow flies.
If you’d rather not handle the winterization of your in-ground, above-ground, or other sprinkler system, Lawn Love can connect you to the best sprinkler system pros near you. Let an expert drain and prepare your system for freezing temperatures, saving time and preventing costly repairs!
Main Image Credit: Mikhailov Studio / Adobe Stock Free / License