How to Winterize Your Sprinkler System

An in-ground sprinkler system holds water in its pipes and valves year-round unless you drain it out before winter. Once temperatures drop below freezing, any water left sitting in those lines expands as it turns to ice, and that expansion can crack pipes, valves, and sprinkler heads buried throughout your yard, damage you won't even discover until you turn the system back on in spring.

What you'll need

• Adjustable wrench
• A basic understanding of your system's shutoff and drain valve locations
• An air compressor rated for the job, if you're attempting a full blow-out yourself (more on why this needs caution below)

Winterizing steps

1. Shut off the water supply to the irrigation system. Find the main shutoff valve dedicated to your irrigation system, separate from your home's main water shutoff, and close it fully. This stops any new water from entering the system while you drain what's already inside.
2. Shut off the automatic controller. Set your sprinkler controller to "rain mode" or off entirely so it doesn't try to run a cycle over the winter with no water pressure behind it, which can damage the solenoid valves.
3. Drain the system using manual valves, if your system has them. Many systems include manual drain valves at the low points of the piping. Open each one and let gravity pull the water out of the lines. Also open any drain caps on backflow preventers or valve assemblies to release trapped water there.
4. Consider whether a full blow-out is realistic for you to do yourself. Some systems don't have gravity drain valves and rely entirely on compressed air to force remaining water out of the lines, a process called a blow-out. This is the step where most homeowners should pause.
5. Insulate anything exposed above ground. Wrap any exposed backflow preventer or above-ground piping with insulating covers or foam sleeves rated for outdoor use, since these components are more exposed to cold air than the buried lines.

Why the blow-out step is different from the rest of the job:

• Using the wrong air pressure or the wrong size compressor can damage sprinkler heads, valves, and pipe fittings from the inside, sometimes without any visible sign until the system fails the following spring.
• Blowing out a system safely means running air through each zone individually, in the right sequence, and knowing when to stop, not simply connecting a compressor and opening every valve at once.
• Residential air compressors from a hardware store are often underpowered or, in other cases, capable of delivering more pressure than certain irrigation components can handle safely.

If your system relies on manual drain valves you can access and open yourself, you can likely winterize it without a blow-out. If it requires compressed air to fully clear the lines, this is the point where professional equipment and experience make a real difference.

Signs your system wasn't winterized properly

• Water spraying unexpectedly from a valve box or fitting when you turn the system back on in spring
• A sprinkler head that doesn't pop up or retract properly
• Visibly cracked heads or valve boxes discovered during spring startup
• A noticeable pressure drop across the whole system come spring

Making the call

If your system has straightforward manual drains and you're comfortable locating and operating your main shutoff, you can likely handle the basic draining steps yourself before the first hard freeze. But if your system depends on a compressed air blow-out to fully clear the lines, it's worth having ProFlow Plumbing handle that part with the right equipment and pressure control, since a mistake there tends to show up as a much bigger repair bill in the spring.