I'm sure you're going to get a lot of great replies, but you may be overthinking this a little.

I clean out my system with a shop vac by vacuuming out the water repeatedly, then blowing it out with the air pressure at whatever it can generate. It does fine. When the vacuum won't suck any more water, it's a done deal for the season...

:-)

Thanks morpheuspa. I forgot to state that my air hose is 1/2" and the orfice is 3/8". As always, I appreciate your comments and am sure you are "on it". I also use my same system for blowing out my in-gound pool and I see a few Youtubes where folks are using shop vacs for that job as well. I guess I just have more confidence in a slightly larger system.Regards, Wil

Will-

I asked this same thing a couple years ago....this year I never used my sprinklers because of the rain but here's the response I got:

https://www.houzz.com/discussions/5493996/diy-sprinkler-blow-out

Thanks Joe BigBlue - My post in that discussion is exactly what I've done. I think the CFM is more important than the PSI because I believe the CFM is what you need to push the water out of the system. Otherwise, I am doing what I said then and it seems to be working very well. I still hire the professional for the front 5 zones, but there is no doubt that I can start doing those myself as well. All I need is the right plumbing adapters and I may do that next fall. Using my iPhone connected controller, it takes the work out of this project if you have the right air supply. I have a 4 HP 24 gallon air compressor with a belt driven pump and I will post the maximum sustainable CFM that I can achieve in the next day or so. I believe the water is going out of the lines without issues inasmuch that air is all that I see when the heads retract. But..... proof is in the pudding, so to speak. Tomorrow, weather permitting, I'm going to run a second round through the system and see if any water can be found. Thanks again for your link to the information. Much appreciated.