DIY, really ? Ever blown anything apart :) ?

Assuming you did not buy the compressed air machine, how much for renting one ?

We borrowed a neighbor's air compressor.

keep in mind, The air compressors used by professionals to do a blow out should be trailer mounted. This is far bigger than the standard kind used to power air tools. While with some patience, luck, and a system that doesn't have a whole lot of grade variations, you -can- blow out a system with these... I have found These DIYers may end up replacing split heads or street ells in the spring though. Then there's the guys that rent a trailer compressor and split the cost with the neighbors. you need to know that 150psi is a little much for many systems, and you may turn nozzles into air-powered rockets :) Winterizing isn't rocket-science, but it can be a hassle if you don't know what your doing. A pro is going to take care of it, without you having to be there, and warranty their winterization against frost damage. seems like a good deal for $50-$100 (depends on your system size, and time it takes to do)

I have been blowing out my lines with my shop compressor for as long as I can remember. The big trailers are used for high volume not for high pressure. Even a tiny portable compressor can do 150psi but you have to be creative to get enough volume to blow out a line.

exactly. the shop compressors start out well, but quicky slow down the amount of air they are throwing out. blowouts with these kind of compressors are a little tricky, I think most people shut the air off and on to allow the pressure to build back up for a few good blasts. in contrast, those trailer ones will continuously blow at a high rate, making sure water does not settle back into a depression in the pipes somewhere. ...the DIYer just needs to make sure they don't blow TOO hard, or you'll start to break things ;)

65$ for mine here in Utah. They guarantee no Broken lines or sprinklers from freezing come spring. I have 6 zones.

Ours charges $40 in metro Detroit (Michigan).