Q: We have a chronic mildew problem in our stall shower that is sometimes evident on our plaster ceiling. However, the condition is much more serious in the grouting between the tiles. Fungicidal growths that look like mushrooms, and which grow to as much as 1/2 inch across, sprout from time to time from the grout joint where the floor and the wall meet. I can get rid of this mildew for a while by washing it with a diluted Clorox solution, but the mildew and the growths always seem to come back. The shower stall seems reasonably well ventilated in that it dries out fairly well when not in use. Can you suggest anything?

A: Washing surfaces with a solution of laundry bleach and water usually kills the spores of the fungus that cause mildew, but it may be that the solution you used was too weak. It should consist of about 1 part fresh bleach to no more than 3 parts water. Scrub this on and allow it to soak in for a few minutes, then rinse off with water.

If, in spite of this, the growths you describe continue, it is apparent that the mildew is growing from behind the tile or below the surface, and surface washing won't get rid of it. Sometimes the problem can be solved by scraping out all the old grout along the troublesome joints and re-grouting with a new mildew resistant material.

However, it may be that the dampness is inside the wall or in the material behind the tile (gypsum board for example), and the mildew is growing out from there. The only permanent solution for this condition is to correct the dampness problem and then treat with a mildewcide solution such as described above. This may mean actually taking all the tile off so you can get at the surfaces or materials behind the tile.

Q: I have been having trouble for some time with condensation on the windows of my house, which is about 20 years old. There are storm sashes on all the windows. The condensation occurs between the two panes of glass, mostly on the outer glass, yet the small ventilation holes on the storm sash are all open. Can you suggest a solution?

A: Two steps can be taken to alleviate the problem, although in very cold weather you may never get rid of condensation. First, make sure the weather stripping on the inside of the main window is good, or add new weather stripping to keep the warm, moist air on the inside from escaping to the outside, where it condenses on the cold outer glass. Second, you can add another storm window on the inside -- usually plastic that you put up yourself. The extra pane of glass or plastic creates an additional barrier that often solves the problem completely.

Q: I am a retired man and enjoy painting my co-op apartment when the need arises. As a rule the plaster walls require quite a bit of spackling and I find that the large amount of sanding required is tiring. Would it be possible to use a light-duty orbital sander for this job, and if so, what grit paper do you recommend?

A: You can certainly use an electric sander instead of sanding by hand, but I am not sure that it would save that much work. The small units are slow-working, and holding up the extra weight for the time required more than makes up for the efforts saved in hand sanding. If you want to try, I suggest an 80- or 100-grit paper.

I think you are neglecting the fact that if done with even a reasonable amount of care, spackling should require very little sanding when the job is done. You should practice putting the material on so that you need very little sanding after. Spread it on more sparingly with a flexible putty knife, and finish it off by dipping your knife in water for the final smoothing.

Q: We plan to go away for a few months this winter and I plan to drain all the water lines and empty all the drain traps under the sinks and in the toilet bowls. After I drain all hot and cold water lines I will leave faucets open and drain cocks open on the main shut-off valves where the water enters the house. I will also open the drain valve on the water heater. Will this drain everything as far as you can tell?

A: It sounds as though you will be draining the plumbing system completely with the steps you have described, but there is one precaution I advise: Do not empty the traps completely. This would allow sewer gases to escape back into the house through the open pipes. Instead, fill the traps with antifreeze to maintain the seal without danger of freezing.

Questions about home repair problems should be addressed to Bernard Gladstone in care of The New York Times Syndication Sales Corp., 200 Park Avenue, New York, N.Y. 10017. Questions of general interest will be answered in this column but unpublished letters cannot be answered individually.