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Thread: Compressor CFM - HELP!

  1. #1

    Default Compressor CFM - HELP!

    Hello...I would like to blow the lines of my sprinkler system myself. The local irrigation company is charging $110 (includes opening the system as well). I need to buy an air compressor anyway but want to make sure I purchase one that can also handle the irrigation system.

    I've read low PSI and high CFM are what I need. Minimum CFM I believe as posted should be 10 @ 40 PSI. However, I cannot find any air compressor that is capable of 10CFM @ 40psi - Sears, Lowes, Home Depot etc.... I don't want to spend $2000 on a compressor so I was wondering if you really need 10CFM@ 40 or will 5CFM@40 work??? Dewalt has a compressor for about $300 that does 5 CFM @ 40PSI - 4 gallon tank. I also found one capable of 7 CFM @ 40 from Ace Hardware for $370.

    Please advise...I have a small pice of land 1/4 acre and have a 4 zone sprinkler system.

    Thanks for your help!

  2. #2
    Sprinkler Guy Wet_Boots's Avatar
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    Are you capable of handling every aspect of servicing and repairing your sprinkler system? You will never call any professional for a repair? Pros don't use home center equipment for winterizing, because their equipment has to last for thousands of winterizings.

  3. #3

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    Gee. Thanks so much for the insightful comment. Did I say I was a pro? If I were a pro, would I be asking a question here?

    I have to buy a decent size compressor for other reasons and would like it to handle the winterization of my sprinkler system if possible. That's a reasonable thought. It doen't look like rocket science to blow the lines out myself so that's what I'm hoping for so as not to pay $100 every year again.

    Lowes has a 6CFM 10 gallon compressor @ 40psi that I might give a try. If it doen't do the job, then I can always call that "PRO" as you so put it.

  4. #4
    In the Trades Bob NH's Avatar
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    The size of compressor needed to blow out a system depends more on the tank size than the compressor size. The best way is to pump the tank up to maximum pressure and then dump it into the pipes by opening a ball valve very quickly.

    You need to get enough velocity going through the pipes to entrain all of the water in the low spots. It may be most effective to blow out each zone separately.

    After you get most of the water out you might be able to get a good flow through it by adapting a leaf blower to the main supply pipe. A leaf blower has a lot of flow but limited pressure.

    You can tell if it is working if you get air flowing out of the sprinker heads.

    With respect to the question earlier in the thread about doing things yourself:
    Homeowners with irrigation systems, wells with pumps, water treatment/softening equipment, and similarly complex systems should learn how they work, how to troubleshoot them when there are probelms, and how to maintain them. Otherwise they will spend a lot of money every year for service calls to deal with things they could do for themselves. That is ok if the expense doesn't stress your economic situation, but $200 minimum service calls can be a real drag on your life style if you have to call someone every time something hiccups.

  5. #5
    Jack of all trades frenchie's Avatar
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    If you go zone-by-zone, instead of all at once, you can get by on about 5 or 6 CFM. At least that's what my irrigation system installer told me. And it's worked fine for me these last two years. Just takes longer.

    Bob, I'm not velocity makes any difference. My tank's too small (5 gallons) to flush even one zone out in a single shot, I have to run it for awhile to get all the water out... but it works.

    My irrigation guy, as I mentionned in another thread, doesn't even have a tank on his compressor. He just carries the motor & piston. He says that you're turning the whole system of pipes into one big compressor tank, so the tank on your compressor is redundant.
    Master Plumber Mark:

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    it smells like......victory......

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  6. #6
    Sprinkler Guy Wet_Boots's Avatar
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    Quote Originally Posted by hotzorro View Post
    Gee. Thanks so much for the insightful comment. Did I say I was a pro? If I were a pro, would I be asking a question here?

    I have to buy a decent size compressor for other reasons and would like it to handle the winterization of my sprinkler system if possible. That's a reasonable thought. It doen't look like rocket science to blow the lines out myself so that's what I'm hoping for so as not to pay $100 every year again.

    Lowes has a 6CFM 10 gallon compressor @ 40psi that I might give a try. If it doen't do the job, then I can always call that "PRO" as you so put it.
    The point of my comment would be that you can be effectively removing yourself from contention (for skilled repair services), when you aren't a regular winterizing customer. No problem if you will handle every aspect of the system maintenance yourself.

    If you have to have a compressor for other reasons, then buy a good one. If you believe that means Lowes or Home Depot, then look harder. Doesn't mean they can't have a decent product to offer, but they aren't selling compressors to anyone who depends on one to work when it has to.

    One absolute, though, is to not buy a 'oil-free' compressor. Cast-iron compressor pumps will outlast them by far.

  7. #7

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    Thank you everyone for your feedback. I'm going to order the Porter Cable 3151 compressor. It will work fine for my power tools and I think it will work well on the sprinkler system. It has a 4.5gal tank and has 7.8CFM@40psi

    This is the highest CFM that I can find at a reasonable price and the compressor won't take up too much space in my garage. I'll probably have to let the take charge a few time while blowing out each zone.

  8. #8
    Jack of all trades frenchie's Avatar
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    Don't get that one. Get the one that's almost the same, but without wheels, and a seperate handtruck if you need to roll it around.

    I got that one - it sucks to roll around - be much better off with the wheel-less model, permanently strapped to a handtruck.

    Specifics? The wheels have really low clearance (forget pulling it up or down stairs, or over rough ground); the handle is too short (hello, sore back); and the bolts where the fold-out handle pivots, vibrate loose every time you run the compressor.
    Master Plumber Mark:

    there is nothing better than the
    manly smell of WD 40 in the air
    while banging away on brass with a chisel and hammer...

    it smells like......victory......

    do not hit your thumb...
    __________________
    Just so everyone's clear: I'm the POODLE in the picture ("french", get it?) The hot woman is my wife.

  9. #9
    In the Trades Gary Swart's Avatar
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    I have a 7-1/2 hp single stage compressor with a 60 gallon tank. This is a stationary unit and I have piped my shop with copper pipe. (Thank God before copper prices went out of sight!) My sprinkler system has 5 zones. To winterize it, if first remove the back flow preventer (2-1" copper unions) I then attach an adapter I made to the output side. This adapter has a ball valve and an air hose coupler. I attach a long air hose from the shop to this. To blow the system out, I open each zone individually and turn the ball valve on. I exhaust the air in the tank, close the valve, recharge the tank, and blow again. This takes a bit longer than the pro with the industrial compressors who can blow the entire system with one shot, but works and sure is cheaper!

  10. #10
    DIY Junior Member
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    Default Air Compressor to Sprinkler Adaptor

    You can find simple instructions on how to winterize your sprinkler system here. It is in pdf format so it is printer friendly. The adaptors to connect air compressor to garden hose are available at this Air Compressor Adaptor Site.

    Jeremy

  11. #11
    In the Trades Gary Swart's Avatar
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    You don't need to send away for some fancy fitting to adapt a garden hose. All you need is a pipe to hose adapter that is available at any plumbing supply, and a bushing to thread an air fitting into. Note that you do not pressurize this adapter so there is not need to worry about it holding high pressure. Open faucets before turning the air on.

  12. #12
    DIY Junior Member cn90's Avatar
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    I have a 5-gallon 130 psi compressor I use for nail guns etc.

    I understand all those issues of professional air compressors psi and CFM (Volume matters b/c time is money for professional landscapers) but I am in no hurry as a home owner.

    This is what I plan to do:

    - Fully charge Air Compressor
    - Set Regulator to 60-70 psi.
    - Bleed One Zone at a time.
    - Let the Air Compressor fully "recover" before next bleed.

    Any advices?
    Last edited by cn90; 10-09-2009 at 10:54 AM.

  13. #13
    In the Trades Gary Swart's Avatar
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    Never turn air into a sprinkler system with the zone valves closed. While the risk may be minimal, that could blowout your zone valve and/or pipe. Pressure is not the key to blowing sprinkler lines. Obviously you must have some pressure, but what is really important is volume of air. A large tank with a compressor that has a low pressure will work better than a small tank and a high pressure compressor.

  14. #14
    Sr. Systems Engineer, Biotech
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    I've got what would be considered to be on the lighter-end of an idustrial compressor that can provide 11 CFM @ 90 psi all day long. When blowing out, I will connect to the irrigation system through a regulator set to about 40 psi, set a program to run each zone for 3-5 minutes and let it go. It takes about 45 minutes to make sure the entire system is blown out good. This doesn't kill my compressor and in seven years I've never had a problem.

  15. #15
    DIY Junior Member cn90's Avatar
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    Somewhere on the internet, I gather that you don't need a tank, so a compressor alone is fine.

    Has anyone tried this?
    http://www.harborfreight.com/cpi/cta...emnumber=93785

    Single stage twin cylinder pump.

    Air delivery: 14 SCFM @ 40 PSI, 11.5 SCFM @ 90 PSI
    Proven belt driven design for excellent compression and smooth running
    Two mufflers and two high efficiency intake filters
    Oil viewing window and drain plug
    Ball bearing check valve release
    Effective splash lubrication system keeps pump running cool
    Aluminum construction with cast-iron cylinder sleeve

    Max. pressure: 140 PSI; Max. speed: 1200 RPM; Flywheel: 10-1/4'' with V-groove; Four 13/32" mounting holes (1/2" x 14 TPI)
    Weight: 23 lbs.

    ITEM 93785-3VGA

    $89.99

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