Pipes burst because of the pressure that's exerted when water freezes. It can exceed 2,000 pounds per square inch, so it's no match for metal or plastic pipes, which will burst under this extreme pressure.
Ice particles can also cause problems in your pipes by blocking valves or other areas.
What should you do to protect your pipes?
When temperatures are expected to drop to about 20 degrees, you should take the following steps to keep your pipes from bursting:
Leave water dripping or trickling slowly from your faucets. This helps reduce the buildup of pressure inside your pipes. If the water stops dripping, it could mean that ice has formed and is blocking the pipe, providing a good indication that the situation needs close monitoring.
Closely monitor all pipes. This is especially important for those located in attics, crawl spaces and outside walls and near electrical outlets, because these have the most exposure to cold temperatures.
Learn where your water shutoff valve is located. That way, you'll be able to shut it off in case your pipes burst. If your home is built on a slab, your shutoff valve is probably near your hot water tank. If you have a basement, you'll probably find your shutoff valve there. And if your home is built on a crawl space, the valve will probably be located there, under the front wall of your house. If all else fails, you can also shut the water off at the city water line's covered box near the front of your home.
Open cabinets beneath sinks. This is especially helpful if the sink is on an outside wall, because this helps keep the pipes underneath it warmer.
Use an insulating dome or similar covering. This can cover and protect outdoor spigots.
Check the areas around pipes and hoses that come into your home. Look for signs of daylight or outside air that's getting into your home. Block the holes with insulating foam or caulk.
Wrap your pipes. Look for thick foam or fiberglass insulating sleeves, UL-listed heat tape or other insulating products at a home improvement store. Wrap your pipes tightly and secure with acrylic or duct tape, cable ties, or aluminum foil tape or wire every foot or so to make sure it stays secure. Wrapping your pipes isn't expensive, and it can save a great deal of money and aggravation.