How to winterize a sprinkler system to prevent damage

Key points

• Winterize your sprinkler system before temperatures drop below 32 degrees Fahrenheit.
• Winterizing your sprinkler system prevents pipe bursts when temperatures drop below freezing.
• You can winterize your system yourself, but hiring a professional is recommended if your system requires a blowout.

If water remains in your sprinkler system throughout the winter, it will freeze when outside temperatures dip below freezing. Water expands when it freezes, leading to burst pipes. Replacing these underground pipes is time-consuming and expensive, so you should winterize your sprinkler system before temperatures drop.

Winterizing your sprinkler system requires shutting off water to the system, turning off the timer, draining the system and insulating the exposed components. It’s a relatively straightforward job that many homeowners perform themselves, but if you do it incorrectly, you could inadvertently damage your irrigation system.

To winterize your system safely and effectively, you need to know what type of system you have. Some sprinkler systems drain passively, while others require a blowout to drain completely. If you enlist the wrong type of drainage for your system, you could damage it by putting too much pressure on the pipes or leaving water inside that will freeze. This may require costly repairs or a full replacement in extreme cases.

What are the steps involved in winterizing a sprinkler system?

The steps to winterize your sprinkler system are similar for most system types, but the specifics depend on your system’s design. In general, you need to drain the system, prevent backflow and insulate any above-ground components. Here’s how.

Step 1: Turn off the water supply

The first step in winterizing your sprinkler system is disconnecting it from its water supply. Failing to take this step could damage your plumbing fixtures by introducing air into your system, especially if you use compressed air to blow out water and moisture.

Most sprinkler systems are connected to your home’s water supply by a main shut-off valve, which is typically located in a utility closet if you have a basement or crawl space. Closing this main valve cuts your sprinkler off from your home’s water.

Your sprinkler’s main valve may be located near your water meter or along the main line where it exits your house. The location of the main valve should be documented in the materials that came with your system when it was installed.

Step 2: Shut off the control system

You’ll also need to turn off your system’s automatic timer. Set your system to “off” or “rain mode” to prevent it from trying to turn on during the off-season. Some modern sprinkler systems come with a “winter mode” — switch it to this setting, if applicable.

Step 3: Drain the system

Draining your system is the most involved step in winterizing and the one you need to do most carefully to avoid causing damage. There are two main draining methods: passive and blowout draining.

Some sprinkler systems drain passively via drainage valves. These systems are easier to drain because you don’t need access to an air compressor.

There are two types of drainage valves: manual and automatic drain valves. You may find these in an underground access point or in an underground utility closet under your first floor.

• Manual valves: You need to open these valves by hand to drain your system. They’re usually located at the lowest point in your sprinkler system. Opening the manual valves allows water to flow out of your system.
• Automatic valves: Automatic valves open when the water pressure in your system drops. This happens when you shut down the water supply. You won’t have to open the valves manually, but some systems require you to run a cycle without water connected to open the automatic valve. Consult your system’s manual to see what type of automatic valves you have.

Some systems don’t have manual or automatic valves; these require a “blowout” to remove water. This type of system is popular in colder climates, where removing as much water as possible before winter is the only way to ensure your system isn’t damaged by ice.

To blow out a sprinkler system, you must connect it to a compressor and force compressed air through it — blowing any excess water out of the irrigation pipes through the sprinkler heads.

Hiring a pro is best for this type of drainage. If you’re inexperienced or buy an underpowered compressor, you might inadvertently leave water in the system, leading to frozen PVC pipes. Conversely, excess air pressure can cause pipe breakages.

It is also essential that you never hook up a compressor to a system that’s not designed to handle blowout draining. Trying to blow out a sprinkler system that’s set up for passive draining can damage it irreparably.

Step 4: Drain the backflow preventer

If your sprinkler has a backflow preventer, you’ll need to drain it separately from the rest of your system. The backflow preventer may be underground; if so, you’ll need to access it via a hatch.

The steps to drain your backflow preventer depend on the type you have, but the general process is as follows:

1. Shut off the backflow valves: Your backflow system will have valves that determine whether the system is engaged. Open these valves and remove any plugs to drain the backflow system.
2. Open the bleed screws: Some backflow devices have bleed screws. Open these to let the water out.
3. Insulate exposed components: If your backflow preventer system is aboveground, you should insulate it. This prevents cold air from entering the system during winter.

Step 5: Insulate aboveground components

You must insulate any part of your system that sits above the ground to prevent it from freezing. Your system may have come with covers for any aboveground valve boxes, but you can make your own insulating covers with standard insulation tape.

This is another step that’s easy to get wrong, so take your time and make sure the exposed pipes and components are well-insulated. Otherwise, they could freeze. If you’re uneasy about doing this step correctly, consider hiring a professional instead of going the DIY route.

When should I winterize my sprinkler system?

You should winterize your system before outdoor temperatures drop below 32 degrees Fahrenheit. The goal is to prevent water from freezing in the pipes. You’ll avoid system damage as long as your sprinkler is drained and insulated before the temperature hits freezing.

The exact timing will depend on the weather where you live, but a good rule of thumb is to winterize your sprinkler as soon as you’re finished using it for the year. If you know that you won’t need to use it anymore, winterize it right away so that you don’t have to worry about doing it quickly when freezing temperatures hit.

Can I winterize my own sprinkler system, or should I hire a professional?

Winterizing a passively draining sprinkler system is something you can do yourself, although you’ll need to be careful when insulating your system’s exposed parts. As long as you’re comfortable insulating your system’s valve boxes and backflow preventer, winterizing this type of sprinkler system is straightforward and not very time-consuming.

Consider hiring a professional if you need to blow out your system to drain it. A typical consumer-grade compressor can probably generate enough air pressure to blow out your system, but most sprinkler systems require a higher airflow rate than you’ll get out of an affordable compressor. Pressures between 40 and 80 pounds per square inch (psi) are ideal for blowing out most lawn sprinkler systems.

For example, this relatively affordable pancake compressor from Harbor Freight only reaches 2.8 standard cubic feet per minute (cfm) at 90 psi, which is not enough to clear most home sprinkler systems. Flow rate requirements vary, but 20 cfm is the minimum required to blow out a system, according to Air Compressors Direct.

Buying a commercial-grade compressor to blow out your system is expensive and not worth it unless you need a high-quality compressor for other work.

Cost of professional sprinkler system winterization

The cost of irrigation system winterization services varies, but you can expect to pay somewhere between $65 and $125 for professional winterization, depending on the size of your system and where you live.

To provide this cost range, we got prices for sprinkler winterization services from four locations: Long Island Lawn Sprinklers in Hicksville, New York; Pacific Lawn Sprinklers in South Nassau County, New York; Conserva Irrigation in Columbus, Ohio and City Rain Inc. in Seattle.

Many lawn care companies also provide sprinkler maintenance service, so you might be able to have your landscaper winterize your irrigation system for you. If your landscaper doesn’t also handle irrigation system maintenance, look for a dedicated sprinkler company. These companies usually offer service packages that include winterization, spring inspections and service calls to ensure your irrigation equipment works well year-round.

What’s next?

Now that you know what winterizing a sprinkler system entails, decide whether you feel comfortable doing the job yourself. If you’re confident you can drain your system and insulate it well enough to keep it from freezing, you only need to set aside about an hour for winterization.

If you’d rather not risk damaging your system — or if it requires a blowout — hire a professional. You may be able to call on the company that installed your sprinkler system, but any experienced lawn irrigation company should be able to do the job safely.

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