Most Portland winters are wet and mild, which is exactly why so many people skip this job. Then one clear, cold week shows up in December, the water sitting in the lines freezes, and by April there's a cracked valve or a split backflow preventer spraying water across the side yard.
If you want to winterize a sprinkler system properly, the work itself isn't complicated. What matters is doing it in the right order, before the first hard freeze, and paying close attention to the one part that sits above ground all winter. Here's how our irrigation team approaches it for homeowners around Beaverton, Hillsboro, Tigard, and the rest of the metro.
Do You Really Need to Winterize Sprinklers in Portland?
Yes, if your system has any water sitting in pipes, valves, or the backflow assembly. Water expands when it freezes. Buried lateral lines are somewhat protected by the soil, but the backflow preventer, the exposed piping around it, and any shallow runs are not.
We hear "it barely freezes here" a lot. And most nights, that's true. But it only takes a few nights in the low 20s for water trapped in brass and PVC to do real damage. Replacing a cracked backflow assembly almost always costs more than winterizing ever would.
When to Winterize Your Sprinkler System
Once fall rain comes back, your lawn and beds don't need much supplemental water anyway. That's your window. For most Portland-area yards, that means October or early November, ideally before the first freeze or as soon as temperatures start getting close to freezing. It pairs naturally with a fall yard clean-up, since you're already getting the property ready for winter.
Watch the overnight lows, not the daytime highs. A sunny 55-degree afternoon can still drop into the 20s after dark, and that's when the damage happens. It sneaks up on you while you're sleeping, literally.
A good rule of thumb is to winterize the week you notice you haven't needed to run the system in a while. If you still have new plantings or fresh sod that went in this fall, ask your installer whether they need a few more weeks of watering first.
How to Winterize a Sprinkler System, Step by Step
Every system is a little different, so check the manufacturer guidance for your controller and backflow device. Rain Bird's homeowner guide is a solid reference. The general sequence looks like this:
- Shut off the water to the irrigation system. This is usually a valve in the basement, the crawl space, or a box near the water meter.
- Turn the controller off or set it to rain mode. If the timer kicks on with no water supply, you can damage valves.
- Drain the backflow preventer. Open the test cocks and set the ball valves partway open so trapped water can escape.
- Clear the lines. Depending on how your system was built, that means opening manual drain valves or doing a sprinkler blowout with compressed air, one zone at a time.
- Insulate what's above ground. Wrap the backflow assembly and any exposed pipe with an insulated cover.
That last step gets skipped more than any other, and it's the one that protects the most expensive part of the system.
Sprinkler Blowout vs. Draining: Which Does Your System Need?
Some systems are built with drain valves at the low points, so gravity does most of the work. Others need a sprinkler blowout to push water out of the lines. If you're planning a new system, irrigation planning up front is the easiest time to build in drain valves and make every future winter simpler.
A blowout sounds simple, and it's where we see the most DIY damage. Too much air pressure can blow apart fittings, crack sprinkler heads, or damage valves, and running compressed air through a zone that's already dry can overheat the parts. The right pressure depends on your pipe type and the equipment in the ground, so follow the manufacturer limits rather than a number from a video.
If you're not sure which kind of system you have, that's a good sign to have someone look at it once.
The Backflow Preventer Is the Part That Cracks First
Your backflow preventer keeps irrigation water from being pulled back into your home's drinking water. It's also usually made of metal, sits above the ground, and holds water inside several small chambers. That combination makes it the first thing to freeze.
This is also a part of irrigation that has real rules attached. According to the Portland Water Bureau, state law and city code require backflow assemblies to be tested at least once a year by a state-certified tester, and the Water Bureau recommends residential customers test each spring. That makes spring startup a natural time to test, since the system is being recharged anyway.
Olguin C Landscaping holds its own backflow tester certification, so backflow installation and testing stay in-house instead of waiting on another company's schedule. The same small crew that installs your system is the one testing it.
What Happens When You Skip It
Every spring, we get at least four or five calls during the first heat wave from homeowners whose irrigation system won't turn back on. It's almost always the same story. Water sat in a line over the winter, froze, and cracked the pipe. None of those clients had used our winterizing service.
You find out right when the yard needs water most, and a sprinkler repair that could have been avoided in October turns into a rush job.
Common Winterizing Mistakes We See
Most problems come from small skips, not big errors.
The most common one is draining the lines but leaving the backflow uninsulated. The pipes survive, and the most expensive part splits. Another is turning off the water but leaving the controller running, which cycles valves all winter with nothing behind them.
In spring, a lot of folks just turn the water back on without checking for damage. Open the supply slowly, run each zone, and walk the yard looking for geysers, soggy spots, or heads that don't pop up. A soggy spot that never dries out isn't always a broken line, either. Sometimes it's a drainage problem hiding as a leak.
Get Your System Ready Before the Cold Arrives
Winterizing really comes down to getting the water out and protecting the backflow preventer, and doing both before the first real freeze. Skip either one and you're usually paying for it in spring.
If you'd rather hand it off, or you want your system checked and your backflow tested in one visit next spring, our team can help. Take a look at our sprinkler repair and adjustment services or request an estimate, and OCL will walk your system with you.
Frequently Asked Questions
Do you need to winterize sprinklers in Portland?
Yes. Portland doesn't freeze often, but a few cold nights are enough to crack a backflow preventer or exposed pipe that still holds water.
What month should I turn off my sprinklers in Portland?
Most homeowners shut down in October or early November. The key is to do it before the first freeze, so keep an eye on overnight lows once they start dropping toward freezing.
Can I winterize without a blowout?
Sometimes. Systems with drain valves at the low points can be drained manually. Systems without them usually need a sprinkler blowout to clear the lines fully.
How much does winterizing a sprinkler system cost?
It depends on the number of zones, whether a blowout is needed, and whether any repairs turn up. We give a firm price after looking at the system.
Does my backflow preventer need to be tested every year?
In Portland, yes. State law and city code require backflow assemblies to be tested at least once a year by a state-certified backflow tester, and the Portland Water Bureau recommends residential customers test each spring.
