How to Winterize Your Irrigation System (Seattle Homeowners Guide)

Even though our winters are milder than other parts of the country, Seattle still gets cold enough to freeze irrigation lines. If you don’t shut things down the right way, you could end up with cracked pipes, broken valves, and a big repair bill come spring.

Let’s go over the basics of winterizing your irrigation system so you can protect your yard and avoid costly damage.

Why Winterize?

Even one freezing night is enough to burst an unprotected pipe. Here’s what happens:

Water left in the lines freezes and expands

That pressure cracks PVC, splits poly tubing, and damages valves or backflow preventers

Come spring, you fire it up — and boom — leaks, flooding, or a dead zone

So, let’s do it the right way and shut your system down before the first deep frost (usually around late October or early November in Seattle).

Step-by-Step: How to Winterize Your Irrigation System

1. Turn Off the Water Supply

Find the main irrigation shut-off valve (usually near your meter, crawlspace, or basement)

Turn it off completely — this stops water from flowing into the system

If you don’t have a dedicated irrigation shut-off, it might be worth installing one!

2. Shut Down the Controller

If you have a timer/controller, switch it to “off,” “rain mode,” or “winter mode”

This stops the system from trying to run while it’s shut down

Bonus tip: Smart controllers can do this automatically if connected to local weather data.

3. Drain the System

There are 3 main ways to drain:

A. Manual Drain

Some systems have manual drain valves at low points and ends of lines

Open them and let gravity do the work

B. Automatic Drain

If you have an automatic draining system, it will release water when the pressure drops

Just make sure your system is fully depressurized

C. Blow-Out Method (Recommended for Most Homes)

This is the safest and most thorough way — especially for large or complex systems:

Use an air compressor to blow out each irrigation zone

Hook it up to the blow-out port near the main valve

One zone at a time, blow air through the lines until no water comes out

Warning: This needs the right PSI and technique to avoid damage. If you’re not sure, it’s best to call a pro — like me!

Overgrow Yard

4. Insulate Exposed Parts

Wrap backflow preventers, above-ground pipes, and valves with foam covers or insulation tape

For bonus protection, use a backflow insulation bag or old towel + plastic bag combo

Want to Play It Safe? Let Us Handle It

I get it — not everyone wants to rent a compressor, mess with zones, or figure out what all those valves do. If you’d rather just have it done right, we offer full-service winterizing for homes across Seattle, including:

Full blow-out with commercial-grade compressor

Inspection of heads, lines, and backflow

Controller shut-off and spring startup reminder

Peace of mind — no frozen pipe surprises!

When Should I Winterize?

Aim for late October to early November, before we hit regular nighttime temps below 35°F.

Final Thoughts

Winterizing your irrigation system is a simple step that can save you hundreds — even thousands — in spring repair costs. Do it once a year, and your system will last way longer and work like a charm every season.

If you have questions or want to get on our winterizing schedule, reach out anytime.