How to Thaw Frozen Pipes - DIY Plumbing
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Thaw Frozen Pipes

During a freezing cold winter, frozen water pipes are a homeowner’s worst nightmare. Not only are frozen water pipes inconvenient (completely eliminating, or seriously reducing, a home’s water supply), but the pressure built up by frozen water in a pipe can cause the pipe to burst, resulting in serious damage to a home’s ceilings, floors, walls and furniture, and necessary and expensive repairs. 

If, in the middle of winter, you turn on a faucet in your house and nothing comes out, or the water trickles out slowly, it can almost be guaranteed that the pipe has frozen. Upon making this discovery, you must first determine whether or not the pipe has ruptured. If the answer is yes, turn the water off immediately and contact a licensed plumber.

If, however, you are lucky, and the frozen water pipe has not yet ruptured, do not wait for the inevitable.  Act immediately to thaw the pipe by taking the following steps:
Determine whether you have an isolated or more general problem. To make this determination, turn off every faucet in your house.  If water flows freely from all faucets except the one faulty one, you are dealing with an isolated problem and you should move to Step 2.   If, however, the problem is more widespread, and affects a number of faucets, it is best to call a licensed plumber.
Locate the frozen portion of the pipe.  Once you have determined that only one pipe has frozen, you need to figure out where the freeze has occurred. The most obvious place for a pipe to freeze is the uninsulated portion of the pipe, or that portion located along an outside wall or a colder area of your home (such as a basement or attic).  In addition, sometimes pipes located underneath a bathroom or kitchen cabinet also freeze since the warm are in the room does not reach these areas.  In many cases, it is possible to feel along the pipe to determine the exact area where it is frozen.  If, the frozen portion of the pipe is accessible, move to Step 3.  If not, however, a plumber should be contacted immediately.
Open the tap.  The next step in thawing the pipe is to open the faucet that corresponds with the frozen line (i.e. open the cold water tap if the cold water line is frozen and the hot water tap if the hot water line is frozen). By doing this, as the frozen area of the pipe begins to melt, water will flow through the pipe, alleviating pressure and helping more ice in the pipe melt.
Apply heat to the frozen section of pipe.  Once the ice melts sufficiently, water pressure in the pipe will force the ice out.  The application of heat can be done in a variety of ways, including the following, but should always be applied from the faucet toward the frozen areas so that water can flow out of the pipe as the ice melts: 

Once the pipe begins to thaw and the water begins to run from the faucet, keep the faucet open for several minutes, allowing the ice to clear from the line.  You should then turn off the faucet and check the line for leaks.  If a leak is discovered you will need to turn off the main water line and either replace or patch the pipe.
While the above steps will generally work, if, after taking such steps, the pipe still remains frozen, do not take any chances and call your plumber immediately.