The Space Boss wrote:

What is this "blowing system out"?

Hooking up an air compressor and blowing the water out of the lines,
so that the water doesn't freeze, expand, and break the pipes or
fittings.

I have to winterize a weekender mobile home up in Flagstaff (AZ)
when I go up there in the winter. Same concept - shut off water, hook
up compressor to outside hose bib, blow until nothing but air
left in the pipes.

If your sprinkler system is set up for this already, there should
be some point after the main sprinkler supply line shutoff
that you can attach an air line. If not, you'll need to tee in
a fitting for the compressor to attach to.

Jerry