How to Winterize Your Sprinkler System (Blowout & Draining Guide)

Quick Answer

Quick answer

Winterizing an irrigation system means removing or protecting any water that could freeze inside the system. For most residential systems in freezing climates, that means:

Shut off the irrigation water supply
Drain exposed plumbing where possible
Protect vulnerable above-ground components
Remove water from underground irrigation lines
Properly shut down the controller
Make sure pumps and other equipment cannot accidentally operate

Some systems are designed to drain naturally. Others require compressed air to properly clear the lines. The important part is knowing what type of system you have before deciding how to winterize it.

Scout tip

Winterization isn't about getting every microscopic drop of water out of the system. The goal is to remove enough water from vulnerable components that remaining water has room to freeze and expand without damaging them.

Why Does an Irrigation System Need to Be Winterized?

Water expands when it freezes.

If water is trapped inside a closed irrigation component, that expansion can damage:

PVC pipe
Polyethylene pipe
Valves
Sprinkler heads
Backflow preventers
Filters
Pressure regulators
Pumps
Manifolds and fittings

Some freeze damage is obvious immediately. Other damage isn't discovered until spring startup when the system is pressurized again — often showing up as valves that won't open or won't shut off. That's why proper winterization is especially important in climates that experience sustained freezing temperatures.

Step 1 – Find and Shut Off the Irrigation Water Supply

Step 1

Isolate the irrigation system

Before doing anything else, identify the shutoff that supplies your irrigation system and close it completely. This separates the irrigation system from the home's or property's active water supply.

If you don't know where your irrigation shutoff is, find it before winter arrives. It's also extremely useful to know its location if you ever develop a major irrigation leak during the season.

Don't Forget the Plumbing Before the Shutoff

Closing a valve doesn't necessarily protect the valve itself. If portions of the irrigation supply, shutoff, or backflow assembly are exposed above ground, they may still contain water. Any vulnerable above-ground piping should be properly drained and/or insulated for your climate and installation.

Step 2 – Determine How Your System Is Designed to Drain

Residential irrigation systems generally fall into three categories.

Manual Drain

Manual drain valves are installed at low points in the system. After shutting off the water, the drains are opened and gravity allows water to leave the piping.

Automatic Drain

Automatic drain valves open when pressure in the irrigation line drops. These can remove a significant amount of water automatically after the system shuts down. However, having automatic drains does not automatically mean every component of the system is protected from freezing.

Compressed-Air Blowout

Compressed air is introduced into the irrigation system and used to push water out through the sprinkler heads. This is common in colder climates and can be very effective when performed correctly.

It is also the method where homeowners can most easily damage their irrigation system — or injure themselves — if they don't understand pressure, air volume, and the system layout.

Step 3 – Understand Pressure vs. Air Volume

This is one of the most important concepts for a homeowner to understand before attempting a blowout. A compressor has two important specifications:

PSI = pressure
CFM = volume of air

You need enough air volume to move the water through the irrigation piping. Simply having a compressor capable of producing 120 PSI does not make it suitable for winterizing irrigation. In fact, feeding excessive pressure into an irrigation system can be dangerous.

Technician tip

A small compressor at extremely high pressure is not a substitute for a compressor capable of supplying adequate air volume.

For the general procedure described here, a compressor capable of approximately 10–25 CFM may be required, while regulated pressure should not exceed 50 PSI.

The appropriate limits can vary depending on the piping and equipment installed. Always respect the ratings and manufacturer requirements of the components in the system.

Why Compressed Air Is Different From Water

A common misconception is:

"My irrigation system handles high water pressure, so the same air pressure should be fine."

It isn't that simple. Compressed air stores energy and behaves very differently from water. Excessive compressed-air pressure can create significant stresses and can turn damaged irrigation components into dangerous projectiles.

Never

Connect an unregulated high-pressure compressor directly to the irrigation system
Stand directly over sprinkler heads, valves, fittings, or other components during blowout
Allow the compressor to build extreme pressure in a closed irrigation mainline
Run compressed air into the system without somewhere for that air to escape
Assume the compressor's maximum PSI is the pressure you should use

Safety warning

Compressed-air winterization can cause equipment damage or physical injury when performed incorrectly.

If you don't know the pipe type, system layout, equipment ratings, or how to regulate the compressor properly, this is one irrigation job where hiring a professional can be money well spent.

Step 4 – Locate the Blowout Connection

Systems intended for compressed-air winterization should have an appropriate connection point. This may be:

A quick-connect fitting
A threaded connection
A dedicated blowout port
A capped tee
Another purpose-built connection near the irrigation supply

Ideally, the connection is located near the beginning of the irrigation mainline so air can move through the system toward the zones.

Scout tip: don't improvise a connection

We've seen homeowners try to connect compressors through sprinkler heads, random fittings, or other components that were never intended to be blowout connections. Before connecting anything, understand where the air is entering the system and where it is going.

Step 5 – Relieve the Water Pressure

Step 5

Bleed off pressure before adding air

With the irrigation supply shut off, relieve the existing water pressure before introducing compressed air. This can normally be accomplished by opening or activating an irrigation zone.

You don't want to connect compressed air against a completely closed, pressurized irrigation system.

Step 6 – Blow Out One Zone at a Time

The basic concept is:

Air enters the mainline → irrigation valve opens → air pushes water through that zone → water exits through the sprinklers.

Start with an open irrigation zone so the compressed air has somewhere to go.
Gradually introduce regulated air.
Watch the sprinkler heads as the zone clears.

The sprinkler heads should begin:

Discharging water
Discharging a mixture of water and air
Eventually producing mostly air and a fine mist

At that point, move to the next zone.

Don't Keep Blowing a Dry Zone

More air isn't necessarily better. Once a zone is mostly clear, continuously blowing hot, dry compressed air through it can damage components. Gear-driven rotors in particular use water for lubrication and cooling during normal operation.

Limit continuous blowout of an individual zone to no more than approximately two minutes at a time. Rather than trying to completely clear a zone in one long run, cycle through the system. For example:

Zone 1 → Zone 2 → Zone 3 → Zone 4 → Repeat

Several shorter passes are preferable to continuously running air through one nearly dry zone.

Technician tip: watch the sprinklers

The sprinkler heads give you a good visual indication of what's happening underground.

Heavy water discharge: there's still considerable water in the lateral.
Water mixed with air: you're actively clearing the line.
Fine mist / mostly air: the majority of the water has been removed.

Once you're getting primarily air, move on rather than continuing to blast the zone.

Step 7 – Keep an Escape Path Open

One important principle during compressed-air winterization is to avoid trapping compressed air inside a closed irrigation system.

When transitioning between zones, make sure the system is being operated in a way that doesn't create a closed mainline with the compressor still feeding it. At shutdown, leave an appropriate zone or path open while shutting down the compressor so pressure can dissipate. Only disconnect the compressor after stored pressure has been safely relieved.

Step 8 – Don't Forget Drip Irrigation

Drip zones are easy to overlook because they don't dramatically spray water into the air like sprinklers. They may contain:

Drip tubing
Emitters
Filters
Pressure regulators
Flush valves
Manifolds

These components can retain water. Filters and pressure regulators deserve particular attention because water can remain trapped inside their housings. If the drip system has accessible flush points, they may need to be opened as part of the winterization process.

Be especially cautious about applying excessive compressed-air pressure to drip equipment, which is typically designed for much lower operating pressures than conventional sprinkler components. If your drip zone was already underperforming this season, our drip irrigation troubleshooting guide is worth reading before spring startup.

Step 9 – Protect Backflow Preventers and Above-Ground Components

Above-ground equipment is especially vulnerable because it doesn't benefit from the insulation provided by surrounding soil. Depending on the system, this may include:

Backflow preventers
Shutoff valves
Exposed PVC
Filters
Pressure regulators
Pump equipment

Drain vulnerable components where the equipment design allows it and protect exposed piping appropriately for the local climate. When insulating a backflow preventer, do not block required air openings, vents, or drainage points.

Step 10 – Shut Down the Controller

The controller doesn't necessarily need to be unplugged for winter. Many controllers have an OFF, RAIN, or seasonal shutdown mode that prevents irrigation while allowing the controller to maintain its programming. This is often preferable to completely disconnecting power.

Depending on the controller, removing power may cause:

Time and date to reset
Programming to be lost
Wi-Fi settings to require reconnection
Backup batteries to discharge

Check the instructions for your specific controller.

Does Your Irrigation System Control a Pump?

Protect the pump

If the controller activates an irrigation pump, make sure the pump cannot accidentally run after the irrigation water has been shut down or drained. A pump accidentally operating dry can be damaged very quickly.

Depending on the installation, this may involve disabling the pump circuit or otherwise isolating the pump according to the manufacturer's instructions.

What About the Backflow Preventer?

Backflow assemblies can be some of the most freeze-sensitive — and expensive — components in an irrigation system. Simply wrapping one in insulation doesn't necessarily protect water trapped inside it during prolonged freezing conditions.

The correct winterization procedure depends on the type of backflow device installed. If you're unsure what type you have, take a photo before adjusting anything and send it to Scout for help identifying the equipment.

Common Winterization Mistakes

"My compressor goes to 120 PSI, so I'll use that."

Maximum compressor pressure and appropriate irrigation blowout pressure are two completely different things.

Using a tiny compressor and repeatedly building maximum pressure

High pressure does not compensate for inadequate air volume.

Blowing one zone continuously until absolutely no moisture appears

Once you're getting mostly air or fine mist, move on. Excessive dry-air operation can damage irrigation components.

Forgetting drip zones

Filters, pressure regulators, manifolds, and tubing can retain water.

Forgetting the backflow preventer

Underground piping may survive while the expensive above-ground assembly freezes.

Leaving the irrigation water supply on

Always isolate the irrigation system before winterization.

Forgetting about the pump

An accidentally activated dry pump can turn a successful winterization into an expensive spring repair.

Assuming automatic drains mean there's nothing else to do

System layout, low points, valves, backflow equipment, and above-ground components still need to be considered.

Should You Winterize Your Own Irrigation System?

For some homeowners, absolutely. DIY winterization may be reasonable if you:

Understand your system layout
Know where the irrigation shutoff is
Have a proper blowout connection
Know what piping and equipment are installed
Have access to an appropriate compressor
Can regulate pressure correctly
Understand how to safely operate each zone

But this is also one of those jobs where the equipment required to do it correctly can make professional service worthwhile. If you're planning to rent a large compressor specifically for one annual blowout, compare that cost and effort with what a local irrigation contractor charges.

A Smart DIY Alternative

Even if you decide to hire someone for the actual blowout, there are several things worth learning about your own system. Know:

Where the irrigation shutoff is
Where the blowout connection is
Where the valves are located
Which zones contain drip
Whether the controller operates a pump
Where the backflow preventer is
How many irrigation zones there are

Take photos and label things. That information makes spring startup, future repairs, and troubleshooting considerably easier — and it pairs well with the fundamentals in our irrigation design basics guide.

Frequently Asked Questions

Do I actually need to blow out my irrigation system?

Not every system requires compressed-air winterization. Some systems are designed with manual or automatic drainage. Whether a blowout is necessary depends on the system design and the freezing conditions where you live.

Can I use my small garage air compressor?

Possibly, but compressor tank size and maximum PSI don't tell the whole story. Winterization requires adequate CFM at a safe regulated pressure. A small compressor may simply not move enough air to effectively clear larger irrigation zones.

Should I blow the system out at 100 PSI?

No. The guidance in this article recommends regulated pressure not exceeding 50 PSI. The safe limit also depends on the components and piping installed.

Do I need to get every drop of water out?

No. The goal is to remove enough water that remaining moisture doesn't become trapped in a way that causes freeze damage.

Should I unplug my irrigation controller?

Usually the controller can simply be placed into its OFF, RAIN, or seasonal shutdown mode, depending on the model. This can preserve programming for spring.

What if I have drip irrigation?

Don't forget it. Filters, pressure regulators, tubing, and manifolds can all retain water and may require different handling than conventional sprinkler zones.

Why do contractors use such large compressors?

Primarily because of air volume, not extreme pressure. A larger compressor can move enough CFM to push water through long pipe runs and multiple sprinkler heads while maintaining controlled pressure.

Scout's Philosophy

Scout's philosophy

Winterizing an irrigation system isn't complicated because there are dozens of steps. It's complicated because every irrigation system is a little different. The homeowner who understands their system has a huge advantage.

Before connecting a compressor, understand:

Where does the water enter?
Where can I shut it off?
Where will the compressed air enter?
Which components will the air pass through?
Where will the air escape?
What equipment could still contain water afterward?

If you can answer those questions, winterization becomes much easier to understand. If you can't, that's a good indication to understand the system first rather than simply hooking up an air compressor and hoping for the best.

Not Sure How Your System Should Be Winterized?

Take a few photos of:

Your irrigation shutoff
Backflow preventer
Blowout connection
Valve boxes
Controller
Pump equipment, if applicable
Any drip filters or pressure regulators

Tell Scout what climate you're in and what you know about the system. Scout can help you understand what you're looking at, what needs to be protected, and whether your particular system looks like a reasonable DIY winterization or one that's better left to a contractor.

How to Winterize Your Sprinkler System