We have an ongoing problem with a house we own in Washington state. So far, no one has been able to help.

The water tank to the toilet ''sweats,'' dripping so badly that the floor is always wet. We are on well water and a septic tank. I would imagine it is caused by cold water in a heated room. Do you know of anything that would correct this problem? -- E.C.D.

You are correct in assuming that the sweating is from condensation caused by warm, humid air coming in contact with the cold porcelain surface of the tank. The tank is cold from the well water flowing into it.

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 flush tank. This tempering valve allows you to connect a hot water line to the cool line so that water delivered to the tank will be about room temperature. If the surface of the tank is no colder than the surrounding air, condensation will not form.

Another solution is installing 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 the 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 from the bathroom to the basement.

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 condensation from forming. Just hang the unit in the tank and plug into an electric wall outlet.

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

Another solution to your wet floors is the installation of a drip tray mounted 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.

I have a 10-year-old home with nine dual sliding glass doors facing west. Over the last year, I have noticed moisture build-up and streaking between the panes of several doors. I have attempted to disassemble and clean the stain with little success. The stain appears to be etched into the glass. Is there any way to clean and restore the doors short of replacing the glass? -- J.B.L.

Try removing the stains with warm white vinegar or a solution of oxalic acid. If this doesn't work, try a stronger solution of muriatic acid mixed with water (nine parts of water to one part acid). Wear rubber gloves, goggles and old clothes when working with this highly corrosive mixture.

Pour the acid into the water when mixing. Be careful not to get the acid mixture on any painted surfaces. Use tape to mask off wood framing.

If the stains can't be removed with the muriatic acid mixture, they are probably permanently etched in the glass and the only solution would be to replace the glass panes.

A while back you had a letter about mineral buildup in a cut glass vase and you suggested first using white vinegar, then oxalic acid. I tried both and neither one worked.

Do you have any other suggestions? I have a beautiful, large cut glass vase that looks beautiful with long-stemmed roses that my husband grows, but the mineral build-up hurts the beautiful look. -- W.J.H.

Try the muriatic acid mixture described in the previous question.

If this doesn't work, I suggest that as a last resort you contact an antique dealer who does refurbishing work that includes the cleaning of older, fine glass items. He may be able to help restore your vase. However, if the glass is permanently etched, it is doubtful that the stains can be removed.

While out of town for a few days at Halloween time, our pumpkin spoiled on the fireplace hearth. The rotten pumpkin stained the red brick hearth. How can I remove the stain? -- L.B.

You should be able to clean the brick and restore much of its natural appearance. Cleaning and etching preparations for brick and masonry surfaces are available at large hardware stores and masonry supply dealers; get the kind that doesn't contain muriatic acid and follow label directions carefully. Or use fine steel wool and a strong detergent or mechanic's hand soap containing sand, followed by an ample rinsing with clear water to remove all traces of the cleaner.

If the soiling is too deeply penetrated for removal by this method, rub the brick surface with a carborundum block, available at paint and hardware dealers. This will take a lot of elbow grease, but it should expose a fresh, smooth surface of natural brick.

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