The people who maintain my irrigation system always come around with a
super heavy duty diesel compressor they tow around behind a truck. I
believe it takes more air than ANY shop compressor can produce to blow
out an irrigation system. However, somwhere I recall having heard
that a system can be blown out by reversing an ordinary shop vac.
This sort of makes sense since it is a lot of volume that is required
rather than high pressure. Hope this helps.

Joe