When the temperature falls below 32° Fahrenheit (0° Celsius) inside a house, there is a good chance that water supply lines will freeze. When water freezes it expands 9% and pipes can crack or burst. If a pipe cracks it may not show till the ice melts. If a pipe bursts, gushing water will immediately indicate that there is a major problem. Turn off the water supply to the house by closing the main valve and make the necessary repairs. If this happens while you are away from the house, spilled water can cause water damage running into thousands of dollars.
Potential problem areas where plumbing supply lines can freeze are in outside walls or floors above an unheated crawl space.
As a general contractor and building inspector I have good news for you. Frozen water pipes are 100% preventable! That's right. Even if the furnace quits in the dead of winter whether you are at home or away from it for a few days.
In this article I will explain how to:
- Thaw out a frozen pipe before it cracks or bursts.
- Prevent it from ever happening again.

THAWING OUT A FROZEN PIPE BEFORE IT CRACKS OR BURSTS
One of the first signs of trouble is that there is only a trickle of water or no water at all when you turn on the faucet. If it is a very cold day with blustery winds the pipe is freezing up. To pinpoint the trouble spot use a hair dryer to warm the pipe. With the faucet open start at the faucet and very very slowly move down the line till the water starts to flow again. In my opinion this is the best way to pinpoint the trouble area, forget the light bulb or towel soaked in warm water. Once you know where the freezing occurred you can take steps to prevent it from happening again.

WARNING. Unless you are a professional do not use a blowtorch. The heat may melt the solder making the situation worse or the open flame may come in contact with combustibles and start a fire!

HOW TO PREVENT IT FROM HAPPENING AGAIN
There are several ways to prevent your plumbing from freezing that are effective and simple.
Pipe insulation, out in the open or within walls and ceilings
Exposed pipes in an unheated crawl space can be insulated with pipe insulation or wrapped with electric heat tape. Some electrical heat tape or heating cables are thermostatically controlled so they only kick in when the temperature drops below the freezing point.
If the pipes are located within a wall or floor cavity they can be protected from freezing by installing fiberglass insulation batts.

NEVER place the pipes in the middle of the insulation. The insulation should be installed between the cold side of the insulation and the plumbing pipes. There should be NO insulation between the pipes and the warm side of the wall or floor.

Older homes with inadequate insulation Even though adding insulation may not be practical or financially feasible, there are a few things you can do to prevent pipes from freezing during the cold winter months. - Leaving a trickle of water running from faucets in trouble areas may keep the lines from freezing. - Keeping cabinet doors below the sink open a bit will allow more warm air to reach the plumbing pipes. - Aim an electric heater at the section of wall where the problem seems to be. If these measures are not effective you have no choice but open the wall, add insulation or re-route the pipes to the room side of the wall. Before taking that winter holiday Things can go wrong in the house during the winter while you are away. The furnace can break down (gas, oil or propane), or there can be an interruption in power supply (electric heating). If you are planning a winter holiday, find someone who can keep an eye on the house while you are gone. In case of a power failure or furnace breakdown they can contact a contractor to restore heat before the temperature drops to a point where water supply lines will freeze. This person can also give the house the 'live in' look by removing flyers and mail, shoveling the driveway or leaving tire tracks and footprints in freshly fallen snow. If you are planning to stay away for several months, or even the entire winter season, you may want to check the links printed to the left.