Frozen Pipes: Prevention and Cure

House Doctor | Gary Dymski

January 27, 2000

HOW ARE YOU making out in this bitter cold? Better yet, how's your house making out?

Mother Nature's cold shoulder can cause all sorts of problems for residential and business dwellings, not the least of which is frozen water pipes.

Frozen pipes restrict water flow, and if you don't thaw the clogged area quickly the pipes will burst. A 1/8-inch crack in a supply pipe can release nearly 250 gallons of water in 24 hours, according to insurance studies.

To guard against freezing pipes, insulate drafty areas near pipes and wrap pipes exposed to cold air in foam insulation. To find these drafty areas, you'll have to do a little work, like inspecting along exterior walls and near windows or vents in the basement or crawl space. Both fiberglass insulation and foam pipe wrap are available at home centers and hardware stores.

House Doctor Recent columns

Installation is as simple as trimming fiberglass batting with a utility knife and stuffing it between studs. (It's always wise to wear gloves, a long- sleeve shirt, a dust mask and goggles when working with fiberglass insulation products.) Foam pipe insulation is designed to slide over several sizes (1/2 inch and 3/4 inch copper, for example) and also trims to length with a utility knife. Secure the foam wrap by using duct tape.

If you don't have a shutoff valve to your outdoor faucets (or just forgot to use it at the end of the fall) your exterior faucet pipes are probably vulnerable to freezing. Check areas where pipes exit the basement or crawl space. If you can see the outside around the exit hole, seal with one of the several canned foam insulation products on the market. The foam goes on as a thick liquid and then expands as it hardens to form a near-airtight seal.

If you can't insulate yourself, then open hot- and cold-water faucets to a trickle to prevent freezing. Should your pipes freeze, leave at least the nearest faucet on the line open to release pressure. Then find the clogged area by tracing the pipe from the cabinet near the faucet down to the basement or crawl space. If you can't thaw the area, you should shut off the main water supply until you can contact a plumber.

Thaw the clogged pipe before it bursts using one of three techniques: with hot water, with a heat gun or hair dryer or by wrapping the pipe with an electric heating pad. Boiling water-from a tap not fed by frozen pipes-on the stove and then pouring it over the frozen area doesn't take much expertise, but you'll have to be careful not to scald yourself. Repeat this procedure until the clog frees. If you use one of the other two methods, avoid standing water, which could cause electric shock. For a heat gun or a hair dryer, move the instrument often so the hot air circulates about 8 inches from the pipe. (This will prevent the heat gun or hair dryer from shorting out.)

Don't use a propane torch on frozen pipes. Intense heat applied to a cold area can weaken the pipe or turn water to steam, thereby increasing the pressure in the pipe and the chances of bursting and injury.