How to thaw a frozen pipe
One of the hazards of winter is frozen water pipes. Since water expands as it freezes it creates tremendous pressure on pipes, which in turn can cause them to break and damage your home. To safely and effectively thaw frozen water pipes you must first diagnose where the pipe is frozen.
Start by turning on every tap in the house, including the bath taps. This will help you determine the area of the blockage. If the water in the kitchen sink is frozen but the water in the bathroom sink works, then you are probably dealing with an isolated problem. Once you have figured out which tap contains the frozen line, turn off all other taps.
Locate the main water stop tap, which could be located in the cellar, under the kitchen sink, in the garage, by a downstairs toilet, etc. and turn off the water supply to the house. If you cannot find a stop tap, you may have to turn the water off outside in the pavement. It is important to shut off the water prior to thawing the pipes as a pipe may already have broken under the extreme pressure caused by the frozen line. It's better to have a frozen pipe than a leak you cannot stop!
Now that the water is turned off, you have a few options to thaw the pipe. It is important to be aware that, when thawing a frozen pipe, a heavy application of heat will cause it to burst. The reason is that the heat causes the ice the pipe in the pipe to expand. The best way to thaw out a pipe, is to fill a bucket with very hot water and put some heavy cloths in it. Wring out the cloths and wrap them around the pipe. As soon as the cloths chill, reheat them. In a few minutes you may hear a crackling sound which indicates that the ice within the pipe is breaking out and melting. The mild heat of the cloths is far better than the violent action of a blow-torch. Another good method, if you are able to use it, is to place an electric heater near the pipe.
If the hot towel approach doesn't work, a fan heater or a hair dryer may be the next solution. Point the heater or hair dryer in the general direction of the pipe but DO NOT hold too close or you will heat the frozen pipe too quickly. Once the water starts to thaw and trickle from the tap, you can turn the main water supply back on. Keep working with the heat source and keep the water tap turned on until full water pressure is restored.
If every tap in the house is frozen, you are probably dealing with a frozen main water line that supplies water to the house. Turn on all taps in the sinks and bath and turn off the main water supply. Follow the suggestions in step two but apply the heat directly to the pipe that enters the house.
Long term solutions
If your pipes have frozen once, chances are they will freeze again. Here are some tips to keep your pipes working in all seasons.
Wrap outside water pipes or water pipes located under the house or crawl spaces with an insulation material such as pipe insulation tubing. Even wrapping with old towels or newspaper is better than nothing. Take special care to cover all elbow joints, valve bodies, tees and any other fittings.
When temperatures drop, open up the cabinets under all the sinks in the kitchen and bathrooms to allow warm air to circulate in and around the pipes.
Leave the water dripping in all taps and bath during the coldest weather. Check periodically to make sure the waste has not frozen as this could make matters worse. If you can't check, don't leave the taps on.
Keep the central heating thermostat set at a constant temperature both day and night. If your home is unoccupied during extremely cold weather, keep the thermostat no lower than 12ºC (55ºF).
Never use a heat source with an open flame such as a blowtorch or propane heater to thaw a frozen water pipe as an open flame in a home can present a serious fire hazard. Also, excessive heat from a blowtorch applied to a frozen pipe can cause the water inside the pipe to boil and possibly explode.