One safe method for unfreezing pipes is to use a pipe thawing machine. This machine attaches to the frozen section of pipe via spring-loaded clamps and then heats that section. A homeowner can rent this device from a local plumbing supply store or can purchase one new.
Another safe method for unfreezing the pipes is to use a heat gun. The homeowner simply activates the heat gun and waves it between two of the frozen sections to thaw the pipe.
If the pipe is metal and contains water, the homeowner can use a plumber's torch to unfreeze the water. When doing so, the homeowner must be very brief in applying the torch to the frozen area because of the danger of melting the solder from the copper fitting of the pipe. He should not use the torch if the pipe contains anything flammable.
The homeowner can also use electric pipe heat tape to unfreeze the pipes in a slow, methodical manner by wrapping the pipe with heat tape and then plugging the end of it into an outlet.
If the frozen pipes are in a large enough area, the homeowner can use a portable electric heater to unfreeze them. Because of the low wattage of most portable heaters, this method takes longer than the others.