Caution:
Please read our safety
information before attempting any testing, maintenance
or repairs. Some equipment may rely on a cold water supply and suffer damage without it.
Frozen pipes burst because as water freezes, it expands. With enough expansion, pipes will develop cracks. The cracks may not be visible but they will leak nonetheless when the ice melts. Prevention is the best policy, but if you are reading this, then that warning may come too late. For prevention measures, follow this link.
When trying to thaw a frozen pipe there are just a few steps to follow. Locate the frozen pipe and turn off the water supply to this pipe before proceeding. If there is no water at any of the taps in the house, then the main water line is frozen somewhere between the meter and where the water line enters the house. If there is no water for only one part of the house, then the frozen pipe is probably in an exterior wall or uninsulated crawl space or basement. If the pipe is accessible, inspect it visually and by feeling the pipe for any cracks or splits. If you find damage, you may be want to get repair materials ready before thawing the pipe.
Next open the nearest tap down stream from this pipe. This will allow water to drain out as the ice melts and will tell you when you have succeeded in warming the pipe.
How you heat the pipe depends upon the type of pipe and the location. But in all cases start nearest the tap and work outward.