How to Winterize Your Sprinkler System: The Fall Blowout Guide

Why do Montana irrigation systems need a fall blowout?

Montana systems need a blowout because water expands roughly nine percent when it freezes, and that expansion has nowhere to go inside a sealed pipe. The result is the same as forgetting a soda can in the freezer: something has to give. Our hard freezes start early and run deep, so any water trapped in below-ground lines, valves, or backflow devices is at risk. A blowout forces compressed air through the system to push that water out before the first hard freeze does the damage for you.

When should you winterize in western Montana?

Aim to blow out the system in fall, before the first sustained hard freeze, which in the Bitterroot Valley and Missoula area often means late September into October. The goal is to beat the freeze, not to squeeze the last week of watering out of your lawn. Watch the overnight forecast as October arrives; once nights start dipping well below freezing, the ground begins to lock up. Scheduling early is wise because the cold can arrive suddenly, and reputable crews book up fast as the season turns.

How does a sprinkler blowout actually work?

A blowout uses a properly sized air compressor to push water out of each zone, one at a time. The technician shuts off the water supply, connects the compressor at a fitting, and then opens each zone so the air drives the remaining water through the heads until only a fine mist and then air come out. It is methodical, like clearing each lane of a pool before draining it. Each zone gets its turn at a controlled pressure so the lines empty fully without stress on the components.

Can I just drain the system myself?

Manual or automatic drains help, but in our climate they rarely remove enough water on their own. Low spots, heads, and valves hold pockets of water that gravity drains miss, and those pockets are exactly where freeze cracks start. Just as importantly, using too much air pressure during a DIY blowout can blow seals and crack fittings, trading one problem for another. The right tool sized to your system, used at the right pressure, is what protects the parts you paid to install.

What happens if you skip winterizing?

Skipping the blowout risks cracked pipes, split valves, ruptured backflow devices, and broken heads, and you usually will not discover the damage until you turn the system on in spring. By then a single freeze can have caused repairs across multiple zones, often costing far more than the winterization itself. Worse, freeze damage is entirely preventable and stems from skipped maintenance. An hour or two of work in the fall is cheap insurance against a frustrating, expensive spring.

What should you check in spring before restarting?

When you reactivate in spring, reintroduce water slowly and walk the yard zone by zone. Open the main supply gradually to avoid a pressure surge, then run each zone to check for leaks, geysers, or heads that no longer pop up. Look for soggy spots that hint at a buried break. Catching a small issue at startup is far easier than chasing it mid-summer when your lawn is depending on the system. A professional spring startup pairs naturally with the fall blowout.

Beat the freeze this year. Call HJ Property Care & Tree Service at (406) 493-8300 to schedule a professional fall blowout and protect your irrigation system across Missoula and the Bitterroot Valley.

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