We're looking at a freeze warning here in Austin, TX. Is there anything I need to do tonight to protect the sprinkler system from freeze damage? We've got an RPZ backflow preventer, in case that ends up being important.
All you have to do is leave the water on at a trickle and that will keep the pipes from freezing. If the temps are going to be in the low 20s for more than 24 hours, then you might wrap them in foam pipe insulation for extra measure...and leave the water trickling.