Because water expands as it freezes, frozen pipes can burst, leading to extensive water damage and costly repairs. 

Steps to prevent pipes from freezing in winter:
• Insulate pipes — at least those by windows and doors, and in unheated areas of the home.
• Disconnect your hose from the outside hose bib (outside faucet).
• If prone to freezing, leave faucets dripping slightly — the theory is that running water does not freeze.
• Keep the heat set no lower than 55 degrees Fahrenheit (12.7 degrees Celsius) when you are away.
Too late? Here’s what to do if a pipe freezes:
• Turn on the tap of the frozen pipe and leave it open while treating the pipe.
• Allow warm air to flow safely to the affected area — always use any heat source (electric heating pad, blow dryer, space heater) safely to avoid potential harm and damage to your home and its occupants.
• If you’ve found one frozen pipe, check all the taps in the house — if only a drip comes out, there is likely another frozen pipe.
• If you cannot access the frozen pipe, or if your efforts to thaw it do not work, call a licensed plumber.