How to Winterize Sprinkler Lines: Step-by-Step Guide

When temperatures start to dip, preparing your lawn for winter isn’t just about fertilizer and mowing. One often-overlooked step is winterizing your sprinkler system. Failing to properly prepare your irrigation lines can lead to frozen pipes, cracked fittings, costly repairs, and a delayed start to lawn care in the spring. Fortunately, winterizing your sprinklers doesn’t have to be complicated. Here’s what you need to know.

Water left in sprinkler lines can freeze, expand, and cause damage to pipes, valves, and sprinkler heads. Even underground systems aren’t immune—once the frost line sets in, your system is at risk. Winterizing ensures your irrigation system survives cold months intact and ready to go once spring rolls around.

The best time to winterize your sprinkler system is in the fall, before the first hard freeze. A “hard freeze” typically means temperatures dipping below 32°F (0°C) for several consecutive hours.

• Early to mid-fall (September–October in most regions) is usually ideal.

• Don’t wait until late fall—once water freezes in your system, the damage may already be done.

• If you live in a colder northern climate, winterize earlier. In milder or southern regions, you may be able to wait until late fall, but don’t push it too close.

Pro tip: Watch your local forecast. Once overnight temps consistently hit the mid-30s, it’s time to get the job done.

Locate your irrigation system’s main shut-off valve (usually in your basement, crawl space, or an insulated outdoor box). Turn it off completely to prevent more water from entering the lines. If your valve is outdoors, make sure it’s insulated to protect it from freezing.

Most systems are equipped with a backflow preventer to keep lawn chemicals from entering your drinking water supply. Before winter, you’ll need to drain this unit.

• Open the valves on the backflow preventer.

• Allow any water to escape.

• Leave the valves slightly open throughout winter to prevent trapped water from freezing and cracking the device.

Sprinkler heads, exposed pipes, and drip-system components that sit above ground are vulnerable to freezing. You can either remove them and store them indoors or cover them with insulated covers designed for irrigation systems.

This is the most important (and often most overlooked) part of the process. Simply draining water usually isn’t enough—small amounts of water left in the lines can still freeze and expand.

• Use an air compressor with a minimum of 50–80 PSI (depending on your system’s requirements).

• Connect the compressor to the system’s blow-out port.

• Open each zone one at a time and let the compressed air push water out through the sprinkler heads.

• Continue until only mist or air comes out.

Important: If you’re unfamiliar with air compressors or your system’s layout, it’s often best to hire a professional to blow out your system. Too much pressure can damage sprinkler components.

If you use an automatic controller, turn it off or set it to “rain mode” or “off” for the season. This keeps the controller running without sending signals to the valves.

For extra protection:

• Wrap any above-ground pipes with foam insulation tape.

• Cover valve boxes with insulation.

• Double-check all drains are open and water has been cleared.

And that's it! Winterizing your sprinkler lines is a crucial part of lawn maintenance in colder climates. A couple of hours in the fall can save you hundreds of dollars in repairs come spring. Whether you DIY with an air compressor or call in the pros, the key is making sure no water is left behind to freeze.

By winterizing properly, you’ll protect your investment, prevent costly damage, and ensure your lawn irrigation system is ready to keep your grass green and healthy once the warm weather returns.