Sorry for the lack of info provided. I live in Tennessee, and our "cold" temps range to maybe 5-10deg F. It's not often we go further than that. I should also mention this house was just recently purchased from a previous owner who had the piping designed the way he did. My system is like this:
Public line ---> Water meter ---> Exposed backflow preventer valve ---> House/Cutoff Main ---> Sprinkler Cutoff ---> 2nd backflow preventer ---> Sprinkler system.
I have a main cutoff that will stop water to the entire property just inside the house. Then the line splits to the house and the sprinkler system and I have a separate valve which falls after that and will cutoff water to just the entire sprinkler system. The problem is with the first backflow valve that was installed immediately after the water meter out in the yard. I still don't understand why there was a need for two backflow valves other than the fact there is a slight (5/100ft) incline in the front yard up to the house from the street/public line. The heat tape will need to have a permanent extension cord run (buried) out to this exposed section of pipe and then plugged in, or turned on, as needed?