Mixers: Frozen Lines?

when I drove mixer in the Chicago suburbs we used hot water in the winter time.
we would lock the sprayer open and open the supply valve enough to keep the water dripping to keep it from freezing.
if it did freeze I would open and close the drum water valve real fast to try to break the ice ,
if that didn't work (if there were other trucks on the job) I would use someones hot water to spray on my lines ant try to thaw mine out
at the end of the day I would drain my tank and blow the lines out with the air supply to the tank

 

Kinda OT: Water truck drivers; drain the tank, leave all the spray heads open ( while you have air ) & pull the pipe plug out of the bottom of the spray heads. Check for drains on the manifolds too. Start - stop - left- - right, & you may be okay the next a.m.The water in the morning usually melted any leftover ice...your results may vary.