No attempt should be made to thaw frozen pipes until they have been thoroughly inspected for cracks or splits. A pipe will crack when the water inside freezes—not during the thawing process. If there are any cracks, they should be repaired or a section of pipe replaced before thawing begins. Until the necessary repairs have been made on a cracked pipe, keep it shut off from the water supply and no great amount of damage will be done if it thaws unaided.
The fact that the water inside a pipe is frozen does not necessarily mean that the pipe has split, but it is best to assume that the pipe is defective until proven otherwise by a close inspection.
If the pipe appears to be sound, open all faucets connected to it. This is done to decrease the pressure in the line, should there be an opening undetected. Thawing should begin at the point nearest a faucet, to allow the water to run out.
There are various ways of applying heat to the frozen pipe. Bath towels, dipped in hot water and applied to the pipe, are an efficient and safe means of thawing, if there are no decorations or painted woodwork that might be damaged.
A blowtorch can also be used, provided there are no inflammable objects about. Play the blow torch back and forth along the length of pipe, and avoid concentrating too much heat at one point.
It is possible to use electric heating pads, but this is not recommended because all the conditions for a dangerous electric shock are present. If electric pads are employed, they should be insulated from the pipe with insulation material, and care should be taken not to touch either the heater or the pipe while the current is on.
Frozen drain pipes can be thawed by pouring hot water down the drain or by using chemicals which generate heat inside the pipe. Pour the chemicals down a drain in the same manner as chemical drain cleaners. A very good method of thawing drain lines is to insert a length of small-diameter rubber tubing into the pipe until the end comes in contact with the ice. Attach the other end of the tubing to the spout of a tea kettle containing baling water. The steam from the kettle will flow through the tubing and soon melt the ice.