The first thing to do if you know the nights are getting colder, and your water pipes are not well-insulated, is to turn on a faucet next to the most exposed pipes-- with just a small stream of water. Leave it on overnight or until other preventative measures can be taken. The running faucet is often enough to relieve the pressure that builds up when cold water freezes and expands. If you don't give that pressure a way out-- like through an open faucet, it creates more space by bursting the pipes or creating a leak of its own.
The the other vital piece of information to have is the location of the master water shut-off for your home. It is usually located in a small box outside the house, sometimes buried in the ground, or under the house where the water pipes first enter your foundation. Often in newer or well-planned homes, an auxiliary shut-off valve is located in a closet or in the garage, so that the owner doesn't have to dig around outside to find it. A single water spigot-- with no water outlet, usually-- that controls the water to the whole house. If your pipes do burst, or if you detect a leak, the first thing to do is shut off the water to the house.
Similarly, you want to make sure your outdoor garden hose has been drained, to prevent it from splitting. The next step is to wrap your home's water pipes (and any outdoor water spigots) snugly with insulation. It isn't as important what you use to insulate-- the important part is to make sure the insulation stays dry, and is not touching any electrical wiring or other potentially flammable surfaces. Temporarily plugging air vents in your home's foundation can help retain heat in the home and around your pipes, but it can also create the perfect environment for molds and other toxins.
If you notice the water pressure dropping unusually, it may be a sign that your pipes are beginning to freeze. Leave the faucet on, turn on the warm water as well, and begin taking other steps to prevent disaster. One thing you do not want to do is warm up the pipe too quickly. Steam created by extra-hot water also expands, and can burst a pipe if not given an outlet.
Working back from the faucet and toward the water supply, take steps to SLOWLY and CAREFULLY warm up the frozen or freezing sections of pipe. There are several methods for doing this:
- Carefully, to prevent electrocution, use a hairdryer on low heat to warm up the frozen pipes. Do not over heat the pipes, as metal can boil the water and plastic can melt.
- Carefully, to prevent electrocution, set up a portable heater to blow warm air into the space.
- Wrap rags around the frozen pipes, and pour boiling water on the rags. Keep the wet rags from freezing by putting a slow-but-steady supply of boiling or hot water onto the rags. You will want to place a bucket under the rags to catch water, and prevent standing water or other hazards if you use this method. You must also remove the wet rags, dry the pipes, and then put dry insulation on them, to reduce future problems. Don't let the rags freeze to the pipes.
Foam rubber pipe sleeves or fiberglass insulation with aluminum paper facing for pipes (with aluminum furnace tape) are best for preventing or slowing the freezing rate of water pipes. You'll want to insulate both cold and hot water pipes. Be aware that even pipes in the outer walls of your home are vulnerable to freezing if the weather gets cold enough. Leave the cupboard doors under the sink open a bit to let more indoor warm air reach these pipes.
If you use a well and well-pump, make sure you put an old-fashioned light bulb in the well house, and insulate the walls and ceiling of the housing as well. The light bulb, when on, usually produces enough heat to keep this above-ground portion of your water pipes from freezing. If insulating the well house is a problem, consider piling bales of hay or bags of raked leaves around the well house for the winter. Do not block all airflow, as stagnant air has its own concerns. Also, be aware that well-users should not run more than a tiny stream of water during power outages. It is unwise to flush toilets, wash dishes, wash hands, etc. A well pump usually requires electricity to run, and if you use up the water in the pipes, the well pump may be dry when power returns. This can cause the well pump to burn out, among other unpleasant possibilities.
Another preventative measure is to wrap pipes in special electric heating strips. This is particularly useful for pipes that run through unheated areas, but it is not recommended for plastic pipes, and it does add to your electric bill. Make sure any pipes in the ground outside your home are to code, and buried below the frost line in your area.
A more expensive and more effective solution is to improve insulation in all outer walls, crawl spaces, garages, and attic spaces of your home. This improves the overall heat-retention of the home, and helps the pipes stay above freezing as well. Consider keeping your furnace or heat source on at night, to counteract the drop in temperature outside.
As an environmentally friendly measure, consider keeping a bucket under the faucet when you leave it on. Collect the wasted water, and put it to other use around the house or yard. Splashing cool or luke-warm water on frozen or frosty plants and gardens before the sun hits the plant directly can prevent frost-burn, and prolong the life of the plant.
Here are links to some additional resources: