Step by step in prep and emergency:
1. GET TOUR BOILER INSPECTED
If you know single digits are coming, call a plumber to check all operations on your boiler.
If you cannot get a plumber to come by, or don't want to spend the money, do this simple check on your own:
- Test thermostats. Make sure they're reaching temperature and that they're communicating with the boiler to call for heat
- Bleed your zones. Isolate each zone and run a garden hose from the drain spout and eject any air built up in the lines
2. DONT TURN OFF/LOWER HEAT IN UNUSED AREAS
Leave your heat running and set to at least 65°. DO NOT turn off the heat if you're going away for a long period of time
2. CHECK FOR DRAFTS.
Drafts will freeze a pipe in a jiffy. Check for cold spots
3. RUN FAUCETS IN COLD AREAS
In very cold spots or past problem areas, leave a faucet slowly running over night. Running water is harder to freeze
4. IF CONCERNED, SHUT DOWN WATER AND DRAIN HOUSE.
Your boiler will maintain pressure through one night, but as for supply lines, it's safe to shut down your meter, and drain your house by opening the lowest faucet in the house and leaving it open all night.