qwhat can a homeowner do to prevent the pipes in her house from freezing in cold weather? And if they do freeze and cause flooding, how can this be fixed? - D.P., Merrimac, Mass. AIf a home is built properly, freezing should not be a problem, says Eric Park of Park Plumbing in Natick, Mass. When there is a problem, he says, fixing it may require opening a wall in order to insulate the pipes, or at least blowing in insulation through a hole. If the pipes are reachable, say in a crawl space, foam insulating pipe sleeves can be installed around the pipes. If pipes do freeze, immediately turn off the main water valve, either to stem the flooding caused by burst pipes or to halt the buildup of pressure. If you don't know how and the plumber can't come out immediately, some local fire departments will shut your water off and pump water out of a flooded basement. (Do not use the emergency number for plumbing-related calls.) To thaw a frozen pipe, Mr. Park says, a plumber will often use a machine that sends a low voltage charge through the system to melt the ice and get the water running. If homeowners want to try to fix the problem, the Plumbing-Heating-Cooling Information Bureau in Chicago suggests using a hair dryer, or wrapping frozen pipes in a towel soaked in boiling water, or squirting hot (not boiling) water on the frozen area with a turkey baster. Using an open flame of any kind is verboten. For homes susceptible to frozen pipes, here are some preventative tips: Leave a faucet running (a steady trickle, not a drip) when temperatures dip into the single digits. The highest faucet or the one farthest from the water meter is a good choice. Keep your thermostat set at a minimum of 55 degrees F. Open cabinet doors under kitchen and bathroom sinks to let warmer room air circulate around the pipes. When extremely cold, use a light (with a protected bulb) to warm the area where pipes enter the house or in open crawl spaces. Don't use a light to thaw pipes or if the pipes are already leaking. Beware of the risk of electric shock. Readers: Pose your questions and we'll seek out experts on home repairs, gardens, food, and family legal issues. Send queries to the Homefront Editor, The Christian Science Monitor, One Norway Street, Boston, MA 02115 or e-mail firstname.lastname@example.org CORRECTION In a Dec. 23 (Dec. 25-31 International Edition) story about batteries, the Rechargeable Battery Recycling Corp.'s phone number should have been given as 800-822-8837.