Frosty Weather and Your Sprinkler System
The BACKFLOW PREVENTER in your sprinkler system WILL BREAK IF ICE GETS INSIDE. It is part of its function and design.
TO AVOID BREAKAGE
1. Turn off the water on both sides (inlet and outlet) of the backflow preventer.
2. Drain it, leaving both sides open (this might require a screwdriver.)
3. After the water drains, cover it with a towel or blanket, and then ...
4. Cover all with a plastic trash bag to waterproof it.