How to Blow Out a Sprinkler System





Introduction: How to Blow Out a Sprinkler System

It usually costs $50 to $100 to have your sprinkler system blown out for the winter.  You can do it yourself with a one-time purchase of a $150 air compressor.



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    Thanks for the video Lou, I was able to do it myself with a 3 gallon air compressor. Feeling so accomplished today :)

    2 replies

    When I blow them out, I see the sprinkler heads pop up and empty out water for a couple of minutes, and then eventually blow just air. I'm sure this gets over 90% of the water out of the pipes, which is more than enough to prevent freeze damage.

    I live in the Midwest where temperatures well below freezing in the winter. I have blown out my sprinkler systems this way for 10 years, and have never had a problem.

    Thank you for the video! My boyfriend is a big DIY guy so I'll be sending this over to him. I'll be sure I have a good air compressor and triple check that the sprinkler blowout worked. Am I able to rent an air compressor that's powerful enough to do a blowout or is that something you have to purchase?

    2 replies

    I have always used a simple 4 gallon compressor you can get at a hardware store for under$200, and have never had any trouble. Just let it run 5 minutes per zone.

    How would I go about temporarily defeating the backflow preventer? Air pressure escapes through there preventing me from blowing out the sprinkler lines.

    3 replies

    Something doesn't seem quite right. I suspect your backflow preventer is defective. Mine doesn't do that. There should be eight tiny little valve that you can turn off with a screwdriver that will block anything from going to the backflow preventer.

    Oh! You are injecting air after the backflow valve. You need to inject air before it. You need to shut off the water source to your entire sprinkler system, including backflow valve, and then blow air in just beyond that shutoff. The air should take the exact same path as the water did.

    The backflow preventer seems to work fine. Pressure from downstream of it is automatically released to the atmosphere. Pressure from the supply side is routed downstream to the zone valves. My compressor connection (where I assume a landscape place would connect to) is between my backflow preventer and the zone valves. Air injected there though is back pressure and gets released. I either need to inject my air downstream of the zone valve or I need to install a ball valve between the backflow preventer and compressor connection.


    Yes winterizing a sprinkler system above 60 psi for poly or 80 psi for pvc will damage the pipes and reduce the life expectancy. I would assume HOWTOLOU has a very small yard with low volume requirements (drip or micro or small sprinklers). Removing a good percentage of water out of a sprinkler system requires a higher volume compressor, such as a 185cfm compressor. They are worth about $15,000.

    HowToLou could also have low cost sprinkler heads, lives on a hill where all the water drains to the low spot and runs out of the low sprinkler, or lives in a dry climate and stops watering two to three months before the ground actually freezes or it doesn't get that cold to freeze solid.

    If your pipes are made of LDPE (Poly), the winter breaks will cause small pin holes in the lines where it froze, not a big deal for lateral lines, but any mainline piping with leak continuously. Regardless, the pipes will be damaged, whether you can actually notice it in the future or not is a different story.

    3 replies

    My old boss use to install irrigation systems and blow out his customer's sprinkler lines all the time. He only used a small air compressor and he hooked up to their sprinklers from outside. I never saw him have any problems with it being a small portable air compressor. It just takes more time to do it

    The bigger care compressors don't have a higher pressure, just have higher volume. Ideally, you want to have enough so that you can hit a zone with 60 PSI for 60 seconds or so. I have never had any problems with my 8 gallon compressor.

    HowToLou's yard has 7 zones with 3-4 heads each. He has blown out his lines, using a standard $200 air compressor for 8 years. The winter temps get down below zero sometimes.

    You didn't specify that the pressure in the line should NEVER exceed 50psi. You are not doing a proper blow out. That compressor cannot produce enough air to properly flush the lines. When you blow the system out, the heads should stay UP for the entire 5 min.  If they sink back down, you don't have enough volume available to hold them up.  This is not a lack of pressure, it's a lack of volume.

    1 reply

    I have done it this way for years, and have never had any problems. All the parts are rated to 100 psi, I believe. My compressor is set at about that. While I agree that more volume would help get out every last drop of water, this method gets out the majority of it, as you can see in the video, and I have never had any frozen pipes.