How to Winterize (or Blow Out) Your Sprinkler System

Get Your Irrigation System Prepped for Freezing Temps

Winter’s on its way, and sprinkler winterization should be, too! If you have an irrigation system, it needs attention before low temperatures arrive. It’s not a fun homeowner chore, but it’s better than facing expensive repairs later. 

Know what happens if you skip this? You’re risking frozen pipes, cracked valves, and split sprinkler heads. Plus, you won’t know there’s damage until spring when you turn everything back on.

Ready to winterize your sprinkler system? We’re sharing when to winterize, the different ways to do it, and so much more!

What Does Winterizing a Sprinkler System Mean? 

In short, winterizing is about getting all the water out. Every last drop. The whole point is leaving your pipes, valves, and sprinkler heads dry, so there’s nothing left for freezing temps to wreck.

When people ignore this, the pipes are usually what go first. They crack and split apart. Plastic valves shatter, and sprinkler heads get pushed right out of where they’re supposed to sit because of the ice building up inside.

e’s something to keep in mind about different systems. Most newer ones use either rigid white PVC pipe or flexible black polyethylene. PVC is pretty brittle, so it cracks without much fight when it freezes. Polyethylene can take the cold better since it bends, but even that will rupture if water gets left inside and starts expanding. 

When Should You Winterize Your Sprinklers? 

The biggest thing is that you get it done before temperatures drop below freezing. Of course, exact timing depends on where you live.

Up north, you’re usually looking at late September through early November. If you’re in the mountains or anywhere with high altitude, you’ll need to winterize the sprinkler system even earlier.

Down south, it might be late November or early December. However, some southern regions may not need it at all. Reach out to our partners at Andy’s Sprinkler, Drainage & Lighting or Rainscapes (if you live in Knoxville, TN) to learn more. While most of our partner locations are in southern and coastal areas, they provide additional winterization services in areas where sustained freezes are more likely.

Again, don’t wait until the last minute! Everyone tries to schedule this at the same time, so booking ahead saves you the headache. 

The sweet spot is right before that first freeze hits. If a surprise cold snap sneaks up, just shut your system off at the controller and reach out to us. We’ll make sure everything’s taken care of for the rest of winter.

3 Main Methods to Winterize a Sprinkler System 

Manual Drain Method 

This one’s really hands-on. Start by shutting off the main water supply to your irrigation system. Sounds basic, but people forget this step all the time. Turning off a hose spigot doesn’t count. You need to find the actual main shut-off valve, which is usually tucked away in your basement or utility room somewhere.

After that, open up all the manual drain valves at the low points in your system. Then head to your controller and run one complete cycle with the water already off. This opens up all the automatic valves and gets rid of any pressure stuck in the mainline. Once that cycle finishes, switch your controller to the off position or rain mode.

The best part about this method? It won’t cost you much. The downside? Water loves to hide in low spots or tricky zones, and you might miss some.

Can you do it yourself? Sure, as long as your system has manual drain valves and you feel confident finding them and getting them open.

Automatic Drain Method 

If your system has this setup, it handles part of the job for you. These automatic drain valves kick in and release water whenever the pressure drops below a certain level.

But here’s where it gets tricky. Those valves work great for the lateral pipes and sprinkler heads, but they won’t touch the main supply line. You’ve still got to drain that mainline yourself, or you’re asking for a major break. Also, it’s worth checking any check valves you have, since they can trap water too.

The best part about this winterizing option? It barely takes any work on your end. The catch? It’s not foolproof. You might still need to do a partial blowout just to be safe.

Can you do it yourself? Mostly. But you need to know what your system can and can’t handle.

Blowout Method 

This process includes a big air compressor that shoots compressed air through your pipes to force every bit of water out. It works really well, no matter what climate you’re in or what kind of system you have.

You need specific equipment that hits the right PSI (pounds per square inch) and CFM (cubic feet per minute). Keep in mind that these measure two different things, and you should pay attention to both. 

PSI is air pressure (how hard the air is pushing), while CFM is air volume, or how much air the compressor can actually move over time. You need both dialed in correctly. 

Pressure alone doesn’t get the job done if there isn’t enough volume behind it, so even when your PSI reading looks right, inadequate CFM can leave water sitting in your pipes.

Usually, you’re aiming for 40 to 80 PSI, kept in check with a pressure regulator, and a compressor pushing 30 to 100 CFM. To size that more precisely, a common approach is to divide your largest sprinkler zone’s GPM (gallons per minute) by 7.5 to get a rough CFM target for your compressor. 

It may seem like a lot of math, but it’s fairly easy and seriously important. After all, if you crank the pressure too high, you can damage your pipes or blow them apart completely. Go too low and water stays behind.

This is also why a small compressor usually isn’t enough. It might hit the right PSI, but it typically can’t sustain the CFM your system’s largest zone needs. That means the process either takes way longer than it should or fails to clear all the water, leaving pipes vulnerable to freeze damage anyway. Proper compressor sizing matters just as much as the pressure setting.

Nothing gets your system more thoroughly dry than the blowout method. However, you need specialized gear, and there’s real risk involved if you don’t know exactly what you’re doing.

But do you need a blowout for your irrigation system? Only if you’re located in a region with long-lasting freezes. However, most of our customers live in warmer climates that don’t need blowout services.

Other options for winterization? Temporary removal or insulation of aboveground irrigation components. This safeguards your system from surprise cold snaps and other unexpected weather events.

Step-by-Step Guide to a Sprinkler Blowout 

If you’re dead set on doing a blowout yourself, here’s how. Just be extremely careful.

1. Start by shutting off the water supply to your irrigation system and killing the power to the controller.
2. Next, you need to relieve the pressure in the system. Open up one sprinkler head on whichever zone is farthest from your compressor.
3. Hook the air compressor up to the blowout port on your system. A quick coupling valve (or quick connect) gives you a direct tap into your system’s pressurized mainline, so you can pull water on demand without powering up the controller or activating a specific zone. This point of connection should generally be downstream of your backflow prevention assembly, not through it. Make sure you’re using the right adapter or blowout fitting for this.
4. Air should never be pushed through the backflow device itself. Forcing compressed air through it can damage the assembly and isn’t what it’s designed for. If your system doesn’t have a proper blowout fitting installed downstream of the backflow preventer, that’s a sign this job may be better left to a professional who can either locate an appropriate connection point or install one.
5. Begin with the zone that’s either farthest away from the compressor or sitting at the highest elevation.
6. Now comes the important part. Introduce air slowly. Open that compressor valve nice and easy. Don’t go over 80 PSI if you have PVC pipes (50 PSI for polyethylene). This matters a lot!
7. Keep your eyes on the sprinkler heads. At first, you’ll see a heavy spray of water coming out. Let it keep running until all you’re seeing is a thin, clear mist of air.
8. Move through all your zones one at a time and repeat everything.
9. When you get to the final zone, leave one sprinkler head open while you shut the compressor down and close the valve. This gets rid of whatever air pressure is still hanging around.
10. Disconnect the compressor and make sure all the valves on your system are closed.

Helpful Tips for a Successful Blowout

• Consider going through each zone twice. That way, you know you actually got all the water out.
• Wear proper eye protection any time you’re working with compressed air.
• Never stand directly over sprinkler heads, valves, pipes, or other pressurized components.
• Never leave the air compressor unattended while it’s running.
• Keep at least one irrigation valve or zone open at all times while the compressor is operating.
• Stop blowing air once a zone is dry. Continuing to push compressed air through dry pipes creates friction and heat that can damage the system.
• Try to do multiple short blowout cycles over one long, continuous one to help manage heat and pressure buildup.

DIY vs. Hiring a Pro 

Hiring a professional has some real advantages when it comes to winterizing a sprinkler system. 

• The job gets done more quickly and efficiently. 
• Everything is done safely. Even better, you’re not standing there second-guessing yourself the whole time.
• You’re more likely to avoid costly, surprise repairs. An irrigation expert makes sure everything’s actually empty and protected, which means you’re not firing up your system in April only to discover cracked pipes and busted valves. 

If you want to tackle this yourself, just know what you’re getting into. 

• The biggest risk of a DIY blowout is filling your pipes with too much pressure. It’s easier to do than you think. Plus, if those pipes are damaged, you’re looking at the exact repairs you were trying to avoid in the first place.
• There’s also the chance you don’t get all the water out. Maybe you missed a low spot, or a zone didn’t drain completely. You won’t know until it freezes and causes problems.
• Also, some system warranties get voided if you don’t have professional maintenance done. It’s worth checking before you grab your tools because saving a hundred bucks now isn’t worth losing coverage on a sprinkler system that costs thousands.

Additional Winterization Tips 

Insulate exposed elements. Grab some foam insulation covers and wrap up your backflow preventer and any piping that’s sitting above ground. 

More advice on backflow preventers:

• Most homes have one of two common backflow prevention devices: a PVB (pressure vacuum breaker) or an RP (reduced pressure) assembly. If you’re having a professional blowout done, the compressed air connection should go downstream of this device, never through it. Backflow devices aren’t built to handle that kind of airflow. 
• You may want to drain any trapped water from the backflow assembly itself as a separate step, using its test cocks to release standing water before freezing weather sets in. 
• For the isolation valves connected to the assembly, many pros recommend leaving them partially open (rather than fully closed) over winter, which gives any remaining water some room to expand without cracking a valve or fitting.

Shut your controller down. Either flip it off completely or put it in rain mode. Don’t just yank the plug out. If there’s a backup battery in there, leave it. It actually helps protect the unit from condensation building up inside.

Many controllers offer a rain, off, or dedicated hibernation mode, and these are usually the better choice over unplugging. They pause watering for the season while keeping all your programming (start times, zone run times, etc.) intact. That way, you’re not stuck reprogramming everything from scratch in the spring. 

If you do unplug your controller, just know you may need to redo your settings later. If your controller also operates a pump, take a little extra care here. Some controllers can accidentally trigger a pump even in an off or standby state, so check your manual for any additional steps needed to prevent that over winter.

Deal with your hoses. Unhook all your garden hoses, make sure they’re totally drained, and bring them inside. Then put some insulated covers on your outdoor faucets.

This is also a good time to handle other removable, aboveground components. Hose timers, for example, should be disconnected, drained, and stored indoors just like your hoses, since they’re not built to sit outside through hard freezes. 

If your system uses a rain sensor, check your manufacturer’s guidance. Some benefit from being brought indoors or covered for winter, while others are fine to leave in place. 

Also, if your irrigation system includes a flow sensor or flow meter, keep in mind these may need to be removed before a compressed-air blowout, since forcing air through them can damage the internals.

Look into a smart controller. Some of the newer Wi-Fi controllers have rain sensors and freeze alerts built in, so they can stop the system from running automatically when it gets too cold. This protects your grass, roots, and sprinkler system from serious damage!

Does your irrigation system rely on a pump rather than municipal water pressure alone? That pump typically needs its own separate winterization. This usually means draining it fully and, depending on your climate and pump type, insulating or storing it to protect it from freeze damage, since a frozen pump can be a costly repair.

How to Turn Your Sprinkler System Back On in Spring

Before reactivating your irrigation system in the spring, walk the yard and inspect everything. You want to check your backflow preventer, sprinkler heads, valves, and any visible piping for signs of freeze damage (cracks, warping, or missing parts). If you left any drains or test cocks open over winter, be sure to close those up first.

When you’re ready for spring startup, open the main water supply slowly rather than all at once. Turning it on too fast can cause water hammer, a pressure surge that can stress or damage pipes and fittings that just spent months in the cold. 

Take the same slow approach with your backflow assembly and isolation valves, easing them open rather than cranking them wide open right away.

Once water is flowing, run each zone individually and keep an eye out for leaks, pooling, broken or stuck heads, or any other damage that didn’t show up during your visual inspection. 

Once you’ve confirmed that everything’s running normally, you can reprogram your controller’s schedules and rain settings, so your system is back to watering on autopilot.

Common Winterizing Mistakes to Avoid 

• Forgetting a zone. It only takes one zone with water sitting in it to turn into a huge mess.
• Using the wrong compressor. That little compressor you’ve got in the garage won’t cut it. You need something more powerful for proper sprinkler winterization.
• Ignoring the backflow preventer. It costs a lot to replace, and it needs its own attention. You’ve got to drain it and insulate it separately from everything else.
• Waiting too long. Don’t sit around until you hear the first freeze warning on the news. By that point, every irrigation company in town is getting slammed with calls, so you’ll be stuck waiting.
• Not double-checking. Always take another look at the low points and valves to make sure water isn’t pooling anywhere. It’s worth the extra few minutes.
• Small details that cause big problems. Our irrigation partners can identify leaks and damage before winter weather. They also monitor spray patterns, ensuring water isn’t landing on concrete or hardscapes, which can lead to ice and potential hazards.