# Minimum size air compressor ?



## NJ-lawn

This will be my first year blowing out the sprinkler lines. It's not long runs.....4 zones over 2k 
Sqft. So I'm shopping for an air compressor. What size can I get away with w/o breaking the bank?


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## gr0d

Ive used as little as a pancake compressor to do my 10k 4 zone system for years without issue. Just takes time to let it charge back up.

This year i added another 4 zones to my system so i am going to rent (70 bucks) a tow behind compressor and do my pool lines and sprinklers all in one shot.

With compressors, good volume (cfm) is key. So the higher cfm(cubic feet per minute) compressor you can get is what you should look for. Not necessarily the amount of air the compressor can hold

Im sure others will be around to chime in

Hope that helps a bit


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## ABC123

I use a 3 gallon craftsman at 70psi, takes a while but it works just fine.


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## BCliff

gr0d said:


> Ive used as little as a pancake compressor to do my 10k 4 zone system for years without issue. Just takes time to let it charge back up.
> 
> This year i added another 4 zones to my system so i am going to rent (70 bucks) a tow behind compressor and do my pool lines and sprinklers all in one shot.
> 
> With compressors, good volume (cfm) is key. So the higher cfm(cubic feet per minute) compressor you can get is what you should look for. Not necessarily the amount of air the compressor can hold
> 
> Im sure others will be around to chime in
> 
> Hope that helps a bit


Use a shop vac for your pool lines! Works great. Better volume and maintains decent pressure to get the first chunk of water out.

I use a 26 Gallon to blow my likes on acre property...takes a long time, but does get done.


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## dleonard11122

Not to discount the experience of folks who have done it this way, but filling an air compressor tank and then dumping the contents to blow out a system is not recommended.

https://www.irrigationtutorials.com/winter.htm



> Here's what you should NEVER use. Do not use an air tank filled with compressed air or gas. Do not attempt to create more air flow by filling an air tank, then attempting to blow out the system with large bursts of air from the tank.





> In order to blow the water out of the pipes you will need an air compressor, and it can't be just any air compressor! It needs to be a big, BIG air compressor. Probably bigger than that compressor you already own. In other words that high pressure, low volume compressor you use in the shop is not the right compressor to use! (Did I mention this isn't a project for the average do-it-yourselfer?) How big you ask? For a really small irrigation system (3/4" PVC pipe or 1" poly pipe) you will need at least a 20 cubic feet per minute air compressor. And that is so small that it is not going to do a very good job! Most experts recommend nothing smaller than a 50 cubic feet per minute compressor for a home sprinkler system. Professionals often use a large gas or diesel powered compressor that can discharge over 125 cubic feet per minute of air and can blow out a pipe as large as 3" diameter.


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## GrassOnTheHills

Yeah I'm with @dleonard11122 on this one. It definitely can be done with a standard compressor (there's proof in this thread), but I'd rather pay $70/yr to have a pro do it and leave the liability up to him so I don't need to dig up my lawn next year to repair my blown mainline


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## Vtx531

Any compressor will have a regulator. You would set it to a low pressure (30-40psi) and allow the tank to provide the volume.

No different than a trailer mounted diesel unit besides the fact that those types can provide the volume continuously vs 2 min at a time before the tank gets empty and you have to stop and wait for it to repressurize.

The sprinkler lines and sprinklers don't know the difference.

If you are doing 20-30 system blowouts a day, you don't have time to do the stop-and-wait thing. That's it. Nothing more, nothing less.

Re: Leaving liability up to the sprinkler guy. He will blow out your sprinklers, destroy things, then charge you to fix the leaks and heads next year during the "Spring startup service". How nice!


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## KoopHawk

What @Vtx531 said. He nailed it. It may take you 5x as long as the sprinkler guy to blow it out but you'll get the job done.


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## dleonard11122

Again, not saying I know any better but just quoting what the irrigation bible says on the matter.



> Safety first! Plastic pipe is not designed to hold compressed air! Air does not behave the same way as water in a confined space. Weird and unexpected things happen! Put on eye protection and keep everyone away from the sprinkler heads. If the air becomes trapped by a pocket of water in the pipes it can suddenly "burp" free with enough force to explode the sprinkler heads! Always increase the air pressure in the pipes slowly. Never attempt to blast out the water with a sudden burst of air. If you can't get the water out with a steady flow of air, then you need a higher capacity air compressor.


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## HomerGuy

I usually hire someone to blow out my sprinklers. Last year I did it myself with a 30 gallon compressor my FIL gave me. I had 10 zones and blew out each zone twice just to ensure I cleared any low spots in the pipe. I had no problems in the spring.

I saved about $50 but remember thinking I should have just paid someone to do it. It was a pretty darn boring task waiting for the compressor to catch up.


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## Jacks_Designs

I do my own. Did my neighbors last year too. Air compressor has paid for itself just by blowing out my sprinkler lines. Yeah it takes me a little longer but I feel most people on TLF are DIY kind of people.


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## Lust4Lawn

One year I decided to do this with two horsepower, two stage, 30 gallon air compressor. I blew out the four zones that I had at the time.

Then I decided to schedule blowout service with my local sprinkler company. There was still a lot of water in my lines when blowing out using their tow behind diesel compressor. Even though you might be getting out a good amount of water, unless you compare it directly afterwards with a high CFM compressor you really have no idea where you stand. Now I just call and have it blown out with the larger compressors.


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## hsvtoolfool

> I use a 3 gallon craftsman at 70psi...

Ouch! Keep pressure below 50 PSI to prevent damage to your heads. This especially applies to MP Rotators and spray heads. Perhaps big rotors can withstand higher pressures. I dunno. But I wouldn't exceed the max pressure for you head-type.

> You would set it to a low pressure (30-40psi) and allow the tank to provide the volume.

This! It's all about the CFM, not the pressure. You want low pressure with high volume flow.

I use a cheap old Sears "oilless" 110V 1.5HP compressor with a 12 gallon tank. I fill the tank to full pressure (120 PSI) and crank the output pressure regulator down to 40 PSI. I then blow out each zone until no more water comes out of the heads. It usually takes two or three compressor refills for each zone. Maybe 45 minutes to an hour to blow out 5 zones. No big deal.


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## nnnnnate

I've never blown out my lines and never had any issues. What do you connect the compressor to to blow them out?


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## hsvtoolfool

Many folks in warmer climates don't blow out the irrigation lines. In North Alabama, our "frost line depth" is about 6" to 10", but that's a worst-case based on 100 year temperatures. I've never personally seen the ground frozen more than an an inch or two in our coldest winters. I have friends who have never blown out their systems and never had problems.

I installed my irrigation pipe around 10" to 12" depth, so I technically don't need to blow out my system either. However, I have a backflow preventer, filters, and valves installed above ground for easy access. So I blow out my system to allow any water in these gadgets to drain into the pipes. Besides, I think that it's better for the spray heads if water can't freeze inside them.


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## NJ-lawn

Thank you all for commenting...... I decided to hire a local company to do it for $75. One less job I have to do, $75/year seems very reasonable and the liability is on them.


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