I can provide you with some information regarding this subject.

I recently bought the identical compressor for just that purpose. The problem is with the size of the tank. It cannot hold enough air to keep the pressure up. On top of that the compressor cannot produce enough air to keep up with the outflow into the sprinkler system.

There is one way to aid this process though. If your lines are extremely long (75-100 feet), then I do not think you would be happy with this compressor. But if the run is relatively short, then if you have pop-up heads that only spray when they are up; just put a rock or something on top of all but one in the line that you are spraying out and this alleviates some of the problems of pressure falling too fast. You are in essence just blowing the water out of one sprinkler (not valve) at a time.

Hope that information helps. I ended up getting a compressor with a larger tank and love it. But of course it was three times as expensive--so that will not work for everyone.

Good luck, Brad

Brad

Thanks for the good advice. Question - exactly what size of compressor did you settle on (gallons and CFM)? In your opinion, was it just the size you needed, or slighly too big or too small? As I understand, those parameters are more important to blowing out my irrigation system than is the psi value.

Thanks
Gary

It depends on what your definition of an acceptable job is.

As a rule of thumb, it should probably have wheels if you want to use it for this. Or you could buy a separate air tank and fill it with your small pump, empty it, refill it, empty it etc.

I use a compressor powered by a 4 cyl desiel.

I have seen a few in the 5-7 HP range that could do an job close to professional, but like I said, it all depends on what you are trying to accomplish.

mrpike - thanks for the feedback. Basically, all I want to be able to do is to blow out one zone (5-6 heads) at one time. I don't care if it takes longer than a high-power compressor would. I'll only be doing it once a year. Other than blowing out my system, the only other thing I'll be using it for are simple things like inflating tires, etc. By the way, I do have one acre to irrigate, and so I imagine that my pipes are rather long. But again, as long as I can blow out one entire zone (albeit it slowly), then I'll be happy. I just don't want to do one head at a time while blocking the air (using a rock, etc.) from the other heads in the same zone as the previous post mentioned.

Given that, what CFM, gallon tank size and psi would I need for the compressor?

Thanks again for the advice!
Gary

The problem with using a small air compressor, is when the water clears the first head, most of the small amount of air you are able to push starts to exit the zone. Then you don't have enough CFM to keep pushing the water out the far heads.

The compressors that the pros use is pushing 100+ CFM. At 40-80 psi normally. Large volume, lower pressure.

Will a $100 compressor get water out of the pipes? Sure, just not as much. As long as most the water leaves the heads, and the mains and laterals are not completely full, you will probably be fine.

If you are shopping, get something with a larger tank if you can, if you have only got the budget and room for a small one, well that is fine too. Just fill the system in bursts. Hook up a valve on your hose before the sprinkler. Release all the stored air, once you are down to 10 lbs of pressure,shut the valve. Let the system pump back up and then release the air again. Another option, is to connect an additional air tank in line with the above setup. It will give you more cubic feet of compressed air available. Something like this.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=40057
You could then use a smaller compressor, store up a bunch of air to release all at once.

Definitely not enough cmf need at least 50 to 70 cmf depending on how big your system is. It depending on size of pipes how long of a run of the pipe are from the water source. If you don't do it properly you will have problems in spring