No matter how careful you are, there are times when your pipes will freeze. This is most common in older homes, however, it happens even in more modern homes. If you are unlucky enough for this to happen to you, rather than spending money to have a plumber come out, or worse waiting until the spring, which could potentially allow the pipe time to burst, you can take matters into your own hands.
The major thing that you need to remember when attempting to thaw a frozen pipe is that if you do it too quickly, it may cause the pipe to rupture. If this happens, you are in for much more costly repairs. So, be sure to take your time, do it slowly, and be intelligent in doing it.
The first thing that you should consider doing whenever you have a frozen pipe is run water through the system. While it may appear that all pipes are frozen, you may find that one or two of them might now be. By running the water, you could also help to dislodge the ice jam in the pipe and get the water moving again.
If you know where the frozen pipe is, you can begin heating your pipe by the below directions, but if you don't know where it is, you have to first find the frozen pipe. In order to do this, you have to think of the areas in your home where the pipe would be most likely to come in contact with enough cold air in order to freeze over. This would most likely be in the basement, a crawlspace, or an attic. If the pipe froze, it is mostly likely still cold in that area. If it isn't, the pipe will unfreeze with time anyway and you could just leave it alone and let it happen.
Once you find the frozen pipe and the source, the first step is to find a means for repairing the problem that allowed the pipe to freeze. This could be simply a small hold that developed into your house and the insulation wasn't enough to keep the pipes warm. If you can patch this up, make sure that you do it, until you are able to get a quality repair in that spot. If you don't, your pipes could ultimately burst, which could become quite expensive depending upon the damage done. If you can't patch the area, then shut off all of your water, because you don't want to risk rupturing pipes through your house. Then try to insulate your pipe and warm it up enough to allow any water already in the system to flush out. You'll need to make sure you keep your water faucets on to fully accomplish this.
If you repaired the problem or were able to create a temporary patch, you can now begin thawing out your pipe. The best way to do this is either with a hair dryer or a heat gun. Again remember to do this slowly, keep it fair away from the pipe and as it warms up you can move it closer. Be sure to keep anything flammable out of the way, especially if you are using a heat gun as they can get quite hot. If you keep the faucets open during this process, eventually they will unclog and the water will run through the system.
After you thaw out the area, check it for leaks. Let the water run for a while, wipe the pipe down and clear from condensation, and watch for drips. If there are drips, the pipe possibly cracked when frozen. You'll need to have this repaired before it creates a much bigger leak over time. If it doesn't leak, you're all set and you should be fine. Just make sure that you get the patch taken care of so it doesn't happen in the future.