It’s important that you know when the time has come for you to blow out your sprinkler system. If left full of water, these systems can freeze and cause irreparable damage. So, when should you blow out sprinklers?

The first signs to look for to determine when to blow out sprinklers are autumn leaves and cold temperatures. Blow out your system before the temperatures get below 40 °F, between the months of September and November. Most irrigation systems require air compressors with 55 PSI and 8 CFM to dry out completely.

We have compiled a list of guidelines to follow in order to get this job done right. Follow along to learn how to blow out sprinklers, when you should blow them out, and other options for winterizing your system!

What Does It Mean to ‘Blow Out Sprinklers?’

Blowing out your sprinkler system is very important for yards with any size lawn, especially when the cold weather hits. Residual water and low temperatures can freeze or even rupture your pipes.

Blowing out your sprinkler entails hooking up an air compressor to sprinkler lines and flushing all the water out of the irrigation system. Usually, this is done zone-by-zone, starting at one end of your property and working all the way around to the end. 

Typically there is an ‘air compressor adaptor’ on most sprinkler systems, making it easy for you to hook up your compressor hose.

It’s essential not to damage your sprinkler pipes. To avoid this, make sure to set your air compressor to high air volume and low pressure. Regulator valves can be set to lower PSIs in order to maintain the integrity of your irrigation system.

When Should You Blow Out Sprinklers?

If there’s been a significant drop in temperature, winterizing may soon be necessary. Leaves accumulating around your lawn also signal that Fall has arrived, and now would be an appropriate time for blowing out your sprinklers.

The time to blow out your sprinklers varies by location and climate. The general rule of thumb is to winterize them one week before the temperatures hit freezing. Although, it’s always good to check with your local irrigation company to get specific guidelines. 

If you live in warmer parts of the country like Florida or southern California, winterizing your system may not be necessary at all. Keep an eye on the temperatures as you near the end of Fall to make sure you don’t miss an unexpected stint of cold weather!

How Cold Is Too Cold for Sprinklers?

Blowing out your sprinklers is not only a preventative measure for your irrigation system, but it’s also good for your lawn. Grass and plants go through certain lifespan phases that allow for them to die off in the winter and re-grow during sprouting seasons.

Any temperature below 32 °F is too cold for your sprinklers. It’s better to be safe than sorry, though! Blow out your system before the temperatures dip below 40 °F, as excessive amounts of wind can make the weather feel even colder. 

If you’re looking to mark your calendar, you probably want to winterize your sprinklers between the months of September and November. This allows ample time for your lawn to prepare to enter its winter period.

It’s also never a bad idea to have a professional come out and inspect your irrigation system during this time period. Depending on your system and climate, you may need repairs in order to make sure everything runs smoothly in the spring.

Is Blowing Out Your Sprinklers Necessary?

Like I mentioned above, blowing out your sprinklers isn’t always necessary if you live in a tropical or warmer region of the planet. Deciding whether to do so relies heavily on the temperature outside.

If you live in an area that experiences all the seasons, the answer is: Yes. Otherwise, your sprinkler system will freeze, and the ball valves, piping system, and valve manifold could be ruined. 

Don’t worry- blowing out your sprinkler system should take no more than 45 minutes or so, depending on how big your yard is.

Other Options for Winterizing My Sprinkler System

If you don’t have an air compressor, there are a couple of other choices for preparing your irrigation system for winter.

The other options are:

  • Draining your sprinklers automatically
  • Draining your sprinklers manually

Either is a suitable alternative to blowing out your sprinkler system’s pipes.

Draining Your Sprinklers Automatically

Some sprinkler systems have automatic draining features. This type of sprinkler system uses a spring mechanism inside each valve. When there is no water supply, the pressure drops, and the valves open.

The best way to trigger this is by turning off the supply of water and turning on your sprinkler system. Before pressing ‘On,’ loosen all of the valve caps to dry up the entire system. Let it run for about 20 minutes. 

Most state-of-the-art, modern irrigation systems have this feature!

Draining Your Sprinklers Manually

First and foremost, get yourself some protective eyewear and gloves. Pressurized water is no joke, and you don’t want to hurt yourself.

The steps to draining your sprinklers manually are:

  • First, turn off the sprinkler system’s water supply.
  • Turn off the backflow preventer valves (usually, there are two). If your system doesn’t use potable water, there won’t be any.
  • Locate the lowest positioned valve in your sprinkler system’s mainline, and shut off the sprinkler system’s mainline turn-off valve. 
  • Open any of the other control valves to depressurize the entire system fully.
  • Use caution and open the manual drain valve. This may take a couple of hours- you’ll know the process is complete when water stops trickling out.

Once the last step is finished, you can open the rest of the valve caps to air out the entire system one last time.

How Much Pressure and Volume Are Needed to Blow Out Sprinklers?

There are certain air compressor capabilities needed in order to blow out a sprinkler system effectively.

Generally speaking, it takes about 55 PSI (pounds per square inch) and 8 CFM (cubic feet per minute) to completely and properly blow out a sprinkler system. Anything more or less will render the technique ineffective or damaging.

Most portable air compressors have this type of pressure capability but lack the CFM ability. Attaching another receiver tank to your machine can help combat this issue.

This 60-gallon air compressor has plenty of volume output. You can use a smaller device; it will just take longer and require more than one cycle.

How Do You Blow Out Sprinklers?

Blowing out your sprinklers takes some finesse, but it’s probably the most efficient method.

The process is as follows:

    1. Turn off the main water supply and backflow preventer.
    2. Drain the water out of the hose bib using a bucket.
    3. Next, hook up your air compressor tubing using a compressor adaptor and one of the test cocks on the backflow preventer.
    4. Open another test cock or hose bib on the outer pressure vacuum breaker to release more water.
    5. Turn the first sprinkler zone on (start with the farthest one away from the mainline).
    6. Open the valve connected to your compressor BEFORE turning it on. If you turn the compressor on first, you risk ruining the pipes.
  • Note: You will need about 55 PSI (air pressure) and 8 CFM (air volume) to blow out all of the water. Set your air compressor to kick off at 60 PSI, as you don’t want to ruin the sprinkler system.
  1. Run all of the water out of zone one until no more mist from the sprinkler heads is visible.
  2. Detach your air compressor from the first zone, close the valve, and repeat this process until you’ve cleared out all of the zones.
  3. Open all of the test cocks to drain every last bit of water.
  4. Finally, leave the isolation ball valves half open for the winter months!

If your system doesn’t have an air compressor adapter, check out this video detailing how to make your own jig!

The Bottom Line

As winter approaches, it’s time to start thinking about when to blow out sprinklers before the cold months set in.

The first sign that you should blow out your sprinklers is when autumn leaves begin to fall from the trees, and cooler weather becomes noticeable. Most pipes with water inside can’t withstand temperatures below 32 °F. As a precautionary method, perform a blowout before it gets below 40 °F.

It’s important to mention that most of the portable, at-home air compressors don’t have the ability to clear sprinklers in one cycle. That would require at least 55 PSI and 8 CFM. There are some other options available for using a smaller compressor, like adding another receiver tank. Just remember- anything less or greater will render the technique ineffective or damaging.

You can also check with your local hardware store or irrigation company for more information on recommended care after it starts snowing. They may be able to help with what type of equipment you need if winters are particularly harsh where you live.

If you’re wary of performing this technique by yourself or don’t have an air compressor at home, call in a pro to get the job done for you!