During winter months, water inside plumbing can freeze and, in the worst cases, crack or burst pipes. Not all frozen pipes break, however, and you can prevent major problems by carefully thawing them out. If a faucet won’t run, runs slowly or you have a blocked drain during cold temperatures, suspect frozen pipes. After locating the frozen pipe, select the proper method for thawing it.The best way is to first open all the faucets to release any pressure in the lines. If you can get to it; turn off the valve before the problem pipe you want to thaw. If the pipe has already burst, then you need to repair that section (if there was pressure then there might not be a burst situation.) Look around for signs of water leakage.
Now you want to warm the pipes--don't rush this. Open cabinets to let the house's heat get to the pipers if it is a sink that is frozen. If the frozen pipes are inside a wall or in concrete other than hiring a plumber with a pipe thawing machine (assuming you don't have plastic pipes) the only thing you can do is warm up the room and wait.
A hair dryer can also assist, if there isn't any water around the area.
When you have found and repaired the area, then to prepare for next year, either insulate the pipes better or add a thermostatically controlled pipe wrap (to keep the pipes warm in colder weather.) Also consider rerouting pipes within a heated area.
Frozen pipes do not leak until the ice inside of them begins to melt. Damaged pipes will not reveal themselves until you have begun to thaw them. Locate the cutoff valve for the pipes you are thawing before beginning the process so that you can shut off the water quickly if necessary. Once the water is flowing again, check carefully for small leaks. Turn off all faucets, and monitor the water meter for unseen leaks
To thaw pipes that lead from the water main to a faucet, open the faucet so that the water running through the pipe helps melt ice in the pipe. The open faucet will also create an escape for any steam created as you heat the pipe. Apply heat to the frozen area of pipe by moving from the end closest to the faucet toward the main.