Mikepier wrote:

Last week I blew out my sprinklers. I borrowed a compressor from a
friend. Then today while trying to hook up my hose to wash my car, I
accidentally hit the gate valve to my sprinkler feed line and a little
water got in to the PVC line that goes from my hose bib to the
sprinkler manifold under my deck. I was thinking if I poured a little
antifreeze into the line it would prevent any freezing from whatever
little water got in there. Any drawbacks to doing this?
(I have since removed the gate handle so it will not happen again).

I think you'd better check out the following:

http://www.gi.alaska.edu/ScienceForum/ASF6/680.html

Here's an excerpt:

"The freezing point of an anti-freeze/coolant solution depends on the
concentration of the solution, and rises when the ratio of antifreeze to
water exceeds 60%. . . . ethylene glycol, the principal component of
most antifreezes, freezes at 8 degrees above zero, Fahrenheit. It is
only when water is added that the freezing point is depressed."