Stubborn black mold must be dug out

Q. My bathroom and tub surround are completely tiled, with grout in good shape in most cases, but in a few areas such as corners, and where the tub meets the floor, the grout tended to break up a bit, so the tiler caulked over it. And at the floor line, where he used clear caulk, it has turned black. What if I used white caulk instead of clear; would that work?

TIRED OF BLACK MOLD

A. No, it will not work, and caulking is the wrong thing to use, since the grout has stayed intact except in a few places where it was not compacted enough. The tiled corners are always a problem because there is more space behind the corner tiles than elsewhere, and the cure is to keep pressing in grout until no more will press in. It is a matter of being well compacted.

As for the clear caulk that has turned black, that black is mold and is probably under the clear caulk, but it can migrate through almost anything. So, dig all caulking out with a sharp pointed tool, then dig out all old grout, treat that joint with full-strength household bleach, rinse, and let dry. Then insert the grout - compactly. You must rinse the bleach off because bleach is compatible with nothing.

Q. My copper water pipes have developed a green stain that sometimes I can rub off. Some people said it is harmless, another said to cut out a short section of the pipe where the stain is and replace it. What is it? Is it harmful? Do I really have to cut out a section and replace it?

FRANCIS GUARDINO, Watertown

A. Leave it alone. It isn't hurting a thing. It is oxidation, which occurs when water hits copper, causing the green color. The water is not from a leak; it is usually from condensation. The oxidation, the green color, is the same on a copper roof or copper gutters, which turn green from weathering. The patina (that green stain), is actually good for the copper, preventing further oxidation.

Q. There is a rough spot on my stainless steel refrigerator, where I used the wrong abrasive on it. How can I restore it to its original good looks?

DESPERATE

A. First, there are no abrasives I know for stainless steel. There are many stainless steel lotions and polishes on the market. Find one and try it. It will relieve the rough part, but I am not sure how long. I am not enamored of stainless steel appliances. There are numerous taboos on their treatment, and they need special treatments themselves. I get a lot more questions on how to treat stainless steel than I do over old-fashioned (and reliable) painted finishes. The only stainless steel appliance that works is my sink, which is full of tiny scratches but still looks good. At least good enough to me.

Q. I had my chimney checked out by a chimney sweep, who discovered three fireplaces and the heating system venting into one chimney without any flue liners. He said I should shut off the fireplaces (mortar them shut! ) and put in a stainless steel flue liner for the heating system. Do I really have to do that?

BEACON HILL

A. Beacon Hill, huh? That collection of ancient houses probably has more violations of one kind or another per block than any other section of the city. I don't think you have to mortar the fireplaces shut; that was suggested so you cannot use them. You might be able to get away with just using the heating system, but a new flue is a good idea to prevent sections of the chimney falling apart and blocking the flue. One flue liner is expensive, $1,000 and up; three more for the fireplaces would at least quadruple that cost, hardly worth it for the inefficient fireplaces. Besides, there may not be enough room for three more flue liners.

Q. One of my four toilets, all 25 years old or so, started acting very sluggishly recently, not allowing debris to go down easily. I had it reamed out, and it worked a while, but the sluggishness returned. So I put in a new Kohler low-flow, and it worked well for five or six months, then became sluggish. The plumber snaked it again and said the wax ring blocked the drain. So I put in a Toto (with a new ring) , which also became sluggish before long. I'm at the end of my rope. The other three toilets work fine.

AT WIT'S END

A. Toto, too? That is the be-all-and-end-all of toilets, so you can be safe that the problem is not in the Kohler, or the Toto. I think there is a partial blockage in the drain that leads to the main soil stack (the vertical pipe that goes from the basement up through the roof). Since the other three toilets are working OK, they are probably leading to another soil stack, or their drains are clear.

A partial blockage is a comb, rubber ducky, or plastic toy that lets liquids go through but blocks debris. Since the Kohler worked for several months, it is my theory that the debris took a while to back up and block the partial blockage. So you have to look at the drain that goes from the toilet to the stack and possibly the stack itself.

Q. My pull-down attic stairs work well, and the regular hinges are holding up well, but the spring-loaded hinges that keep the door in place have had it - very badly worn. I have looked everywhere without success.

STILL LOOKING

A. I looked in the Brosco Catalog which features two pull-down attic stairs, and I think I saw the hinges you speak of, but they are not sold separately. You could try putting in a medium-duty spring to take their place. Or, if you can find the manufacturer, contact him. Also, I Googled attic stair hinges and got a whole bunch of websites you can check. One of them is by my old friend Bob Vila (www.bobvila.com). You could do the same.

Q. I have many big old, attractive pine trees, 80 to 90 feet high, in my yard. The closest are about 30 feet away. I am concerned that some might fall some day, right on my house. What should I do?

PAT MURPHY, Hanover

A. Everything is green today, and the more trees we save the better. I think some pines and evergreens have shallow root systems, and you sometimes see a blown-down tree with its root system a huge circle of shallow roots, lying helpless on the ground. Pines and other evergreens will resist blowing down if the earth is not heavily saturated and winds are not high at the same time. Call a landscape contractor, landscape architect, or an arborist to help you decide what to do. If the trees are relatively close together, they are helping to hold each other up.

Q. I am getting a lot of condensation on the under part of my sink that is next to my dishwasher, which produces moist air during drying mode, some of which goes into the space under the sink. So much that it is dripping onto the cabinet floor and rotting the wood. How can I prevent that?

NICK, with a problem

A. The wall between the dishwasher and sink cabinet may have a gap at the top or elsewhere, and of course there are holes for the discharge pipe that are not tight. Caulk the pipe holes and glue a cover at the top to make a tighter fit. There will be enough room in the front of the dishwasher for the steam to dissipate. You could have insulation sprayed on the under part of the sink to prevent condensation.

Globe Handyman on Call Peter Hotton is also in g on Thursdays. He is available 1-6 p.m. Tuesdays to answer questions on house repair. Call 617-929-2930. Hotton also chats online about house matters 2-3 p.m. Thursdays. To participate, go to www.boston.com. Hotton's e-mail is photton@globe.com.