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I want to blow out my sprinkler lines before the freezing weather gets here (I am in NJ). I have an air compressor that I can borrow but how do I attach the air compressor line to the sprinkler system to blow it out?

Here is the water line coming out of my house, into the pressure vacuum breaker, and then into the ground where the valve box is located. In previous years I have had someone come out to do it and I know they attach to that spigot in the picture but I am not sure how. What type of adapter do I need to get?

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Just be cautious when using compressed air. While the pressure may be similar to normal water pressure the properties of air are sufficiently different to run the risk of damaging some types of sprinkler heads. I suggest you use no more than 60PSI. You don't really need much pressure anyway but you need a large volume of air to do the job. –  John Gardeniers Nov 5 '10 at 1:48
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3 Answers

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Something like this should do ya just fine. You'd just have to attach it to the faucet you have and shut off the nearest valve. Should redirect the air down your sprinkler system and blow the water out of the sprinklers. You'll probably need to have a pretty hefty air compressor though, it's probably going to take quite a bit of pressure to get through your system if it's extensive.

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What I usually do to blow out lines is just use a simple hand held blow gun fitting for the air line. You can buy one that has a rubber end that fits inside the garden hose valve. This usually fits well enough that I don't need to do anything special.

When that is insufficient, then I do have a short pigtail (a one foot long piece) of hose with a regular air line connector at one end, and at the other end a female garden hose nozzle. You could probably just chop off the end of an old piece of regular water hose, since it will already have the male garden fitting on it. At the other end, I would buy a barbed fitting of the right diameter that would allow me to connect to a 1/4 NPT threaded connector. Then just screw on a ball valve to turn the air on from the compressor when you want it, and to that, screw on a male air line connector. A GOOD hardware store will have all of these things.

The nice thing about a blow-out tool like this is it does not need to take any serious airline pressure because the end of the line you are blowing out is essentially open ended. So a simple piece of garden hose is entirely sufficient. You might even temporarily reduce the regulator on the compressor to about 40 psi to avoid damaging anything from overpressure.

If you don't know how to make this up, then I'd go to a local hardware store and ask for help. Tell them what you need. (Print out this response if necessary.) Go to a GOOD one, not to the big box stores like Home Depot. Find one of those stores where the person running it knows what they have in the store and where to find it, and they know how to use what they sell too. When you do find such a hardware store, support them with your business on a regular basis.

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Following the advice of both @Scott Vercuski and @woodchips I was able to build my own adapter to go from the air compressor to the faucet. The three parts are:

  • 1/4" Air Compressor fitting
  • 1/2" to 1/4" Male pipe to FIP Hex Bushing
  • Swivel hose adapter (3/4" FH to 1/2" FIP)

alt text

The three parts combined look like this: alt text

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Perfect. It is amazing what you can find in a hardware store if you look. The only thing I would add is a ball valve. If you do this often, it is nice to be able to shut the air supply on and off, without shutting off the compressor, and without needing to detach the air hose. As well, the sudden blast of air you can get from opening the ball valve can be helpful to get the last dregs of water out of a line. It would be simply added to the pieces you have, since you can get these valves in a female 1/4 NPT thread. –  user558 Nov 5 '10 at 11:43
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