Q.We had some new closet doors (not the sliding type) installed. Over several months, the doors have begun to bulge in the center. Unfortunately, the carpenter who did the work is no longer available. Do you know what could cause this, and is there any way to straighten the doors?

A.The best way to straighten warped doors is to remove them from their hinges and place them horizontally on supports -- you can use stacked bricks or sawhorses.

Be sure that the bulging side is face up. Then apply pressure by stacking bricks or heavy books on top of the bulged side. Leave the weights on until the door is straightened.

If the bulging is minor, you might try adding a third hinge at the spot where the door is bowed. With time, this can straighten out the curves.

To help prevent warping, make sure the wood is properly sealed, including all edges as well as the sides. Raw edges can be treated with shellac or a penetrating resin, assuming that the side panels are already finished properly. If painting, use a good primer before applying finish coats.

QA.We purchased a vacation home in the mountains. All summer, I have had trouble with the toilet water tanks, which sweat so much that the floor is always wet. I imagine that this is caused by cold water coming in from our well during hot summer days. Is there any inexpensive way to correct this problem?

A.Warm, humid air coming into contact with the cold porcelain is the cause of the sweating.

One of the most effective methods of eliminating condensation is to raise the temperature of the water before it reaches the flush tank.

A specially designed mixing valve is available that can be installed in the cold-water line supplying the tank. This tempering valve allows you to connect a hot-water line to the cold line so the water delivered to the tank will be about room temperature. If the surface of the tank is no longer colder than the surrounding air, condensation will not form.

Another solution is to install a tempering tank. Designed to accomplish the same thing as a tempering valve, a tempering tank is simply a reservoir in the cold-water line supplying the flush tank.

Theoretically, water allowed to stand in this tank will be warmed by the surrounding air. However, this won't work if large amounts of water must pass through the tank within a short time. Also, condensation will form on the tempering tank so this type of installation simply changes the location of your problem.

One of the simplest solutions to a condensation problem involves no plumbing modifications. An electric immersion heating unit with a self-contained thermostat will keep the water in the flush tank at a sufficiently high temperature to prevent the formation of condensation. Just hang the unit in the tank and plug it into an electric wall outlet.

When replacing old fixtures, consider installing a dripless tank featuring two walls with an insulating sealed air space between.

Another solution is to mount a drip tray underneath the tank. This won't stop the condensation, but the tray will catch the moisture and collect it in removable cups or a drain into the bowl of the toilet. The metal or plastic trays can be installed in a matter of minutes.

Q.We have an outdoor stone terrace, and I am having trouble keeping grass and weeds from growing through the stones. Can you suggest something that is not toxic that we can use to prevent this growth?

A.One of the best products available to control weeds and grass from areas like your patio or driveway is Cleanup, also sold (in larger volume) as Roundup.

This type of product is often used along freeways to keep weeds and grass under control. It is simple to use, effective, and does not sterilize the soil.

Q.Is it advisable and practical to paint 40-year-old linoleum? If so, what type of paint should one use?

A.It would not be satisfactory to paint linoleum this old. Your best bet is to remove it and install one of the new vinyl floorings.

One caution: Your linoleum may contain asbestos and this should be checked before removal. Removal of materials containing asbestos requires specially trained and certified technicians because it is a hazardous material when disturbed.

If your linoleum does contain asbestos, you have another option, which is usually less expensive than removal. A plywood subflooring can be safely laid over the present linoleum floor and a new vinyl flooring installed on top of the subflooring.

Contact an asbestos contractor in your area for information on testing and removal.

Send inquiries to Here's How, Copley News Service, P.O. Box 190, San Diego, Calif. 92112-0190. Only questions of general interest can be answered in the column.