In this video, This Old House plumbing and heating contractor Richard Trethewey explains how to prevent frozen pipes and what to do if faced with one.

Here are his step-by-step instructions:

1. Seal air-leaking holes and cracks around home with expanding foam sealant or silicone caulk.

2. Use foam-rubber pipe insulation to protect exposed pipes from cold.

3. Slip foam-rubber insulation over pipe, peel away backing strips, then press the adhesive surfaces together.

4. At pipe corners, miter-cut the ends of the foam-rubber insulation with scissors, then secure the corner joint with foam tape.

5. Before attempting to thaw a frozen pipe, open the faucet.

6. Locate ice blockage, then use heat gun or blow dryer to thaw frozen pipe; don't use propane torch or other open flame.

7. If the frozen section of pipe is inaccessible, use an electric pipe-thawing machine.

8. Find the exposed ends of the pipe, then place one clamp from the machine onto each pipe; the machine will warm the pipe and eventually melt the blockage.