all you need is a 150.00 compressor from Sears/Lowes/wherever. plus you cna use it for other things. no need to go for the big boy unless you plan on using a lot of airtools in a workshop. i use a 125PSI 3 gallon compressor from Sears and i run impact wrench/air ratchet/nailers/air chisels/etc on a regular basis. if it will run them, it is more than enough to blow a little water out of the pipes!

I prefer something with a bigger tank, say 12 gallons to handle longer runs. But, agree you can do it for 200 or less. You may have to purge each zone a couple times.

Be careful! It is VERY easy to blow the seals in the zone valves with the air pressure. Been there, done that. Red

Good point. Although these compressor tanks usually charge up to around 125 PSI, I'd recommend only releasing around 40 PSI of so into the sprinkler lines (which you control by turning the knob on the output valve and watching the gauge).

You might want to install a ball valve after the valves to prevent the air from damaging the diaphragm on the valve. You can also install drains on the pressure side of the valves to drain after you shut the water off to them. I would also turn your valves on and keep them in the on position so they don't build any pressure and damage them as well.

Here is a link that might be useful: do_it_your_self_site