Readers often ask about best bathroom caulk

Q. A few months ago or longer, someone asked about the best bathroom tile grout, which I purchased and really liked. My husband cleaned off the shelf I thought I put it on, and now I can't find the tube and don't remember the name. Would you please refresh my memory and give me the brand name so I may purchase more.

A. I believe you mean caulking, as I don't recall mentioning any special grout - except, perhaps by suggesting that epoxy grout should be used when grouting ceramic tiles. But I don't believe I mentioned any brand. If you are asking about bathroom caulking, I have had good luck with DAP Kwik Seal Plus Premium Kitchen & Bath Adhesive Caulk w/Microban. You may wish to check the DAP Web site at dap.com and click on "Products," "Caulks and Sealants," "Kitchen/Bath." You will see several choices. The advantage of the caulks with Microban is that they contain a mildew-resistant ingredient.

I recently replaced the caulk around our bathtub, and, within a couple of months, it started to discolor and show signs of mold. Is it as simple as not having allowed for enough drying time - less than 24 hours - or may there be another cause for this happening? I used a white silicone caulk designed for bathroom use.

A. Your problem is silicone, the most overrated yet best-marketed product I know. It claims to be guaranteed for 20 or 40 years, but who is going to remember where they bought it, how long ago and retain proof of purchase. Any person in the building trade will say, "I use silicone" as a mark of savvy product knowledge. Silicone is famous for mildewing and not adhering well. It can be peeled off easily.

The best all-around caulking available is polyurethane, which, fortunately, is now more available than it was a decade ago, when it was used mostly in the commercial construction trades. A.H. Harris, with wide distribution throughout the Northeast, has been carrying Sikaflex-1a - my favorite brand - for years. Home Depot carries a different brand as well as some better-stocked building supply houses.

You won't find polyurethane in hardware and paint stores, which are the bastions of silicone. Polyurethane used indoors needs seven days to cure properly or it will discolor when wet, the only drawback of its use. Another product I have had great success with is DAP Kwik Seal Plus with Microban, as mentioned above.

About 15 to 20 years ago we had our windows replaced, vinyl six over six. Yesterday, we noticed that one kitchen window (which is a swing out casement-style window) has condensation between the two layers of glass. Help! We hate to have to replace the entire window (two sections), as they would not match the other windows (four) in the kitchen. Can this be fixed?

A. Here is a helpful suggestion from an Illinois reader: "Recently, the glass in one of our windows broke. We had replaced the windows about 10 years ago. I e-mailed the manufacturer and they told me to take the window out and take it to a window-and-glass place and have them replace the glazing unit. That worked pretty well. They said that the insulated units all come with Low-e, when I specified that. If the windows are in good a condition, take them out one by one and have the glass replaced. The glazing unit and the labor to put it in the sash cost us about $100."

I have a finished basement, and the area under the steps leading to the basement has a foul odor sometimes. You had written about this problem and mentioned a product to use that may help. I cut the article out of the newspaper and put it away and cannot find it. Would you please rewrite about this problem with the products mentioned that may solve the problem? My basement is dry and solid.

A. I have had very good results controlling a variety of odor problems with Magic Zymes, a product that kills odors quite successfully. Order it online at magiczymes.com or by calling their toll-free number at (866) 478-2368. Another choice is Nok-Out, which works differently and has a chlorine base: nokout.com, (888) 551-1927.

I live in the Foothills development in Jericho, Vt., and our 60 houses share a community well. There have been problems with the water, which stained our toilets. I occasionally use CLR to try to get the rust out, but we also have a septic tank. I read that Drano or other chemicals shouldn't be used in septic systems. The stains persist, so I would appreciate any advice you can give.

A. Drano is not a good thing to put in a septic tank, as most chemicals aren't. However, when there is one chemical that solves the problem, and you use it in a small quantity and give it a chance to lose its potency, you should feel OK about doing so. Buy muriatic acid in a hardware store, slowly and carefully pour about a cup's worth in the affected toilet bowl, close the lid and let it stand overnight. The next morning, scrub the bowl with a toilet brush and flush the toilet. The stains should be gone.

Never pour water in a muriatic-containing container; always pour muriatic acid into water. Never use metal tools or containers when using muriatic acid; use only plastic or glass. Be aware that muriatic acid is a very potent chemical; handle it with great care. Wear rubber gloves and eye protection, and don't let it get on any skin or clothing.

I have an unheated concrete garage floor that is moderately cracked. We replaced the floor five years ago, and the contractor said it would never crack again. He put some expansion joints in the concrete after completely removing the old concrete floor and pouring a brand new floor. It looked good for one year, then very small cracks came. My main problem is the flaking of the concrete, mainly under the four wheels of both our cars. The area under the tires has gradually chipped off, leaving holes about 1/4-inch deep, and 2 feet long, in eight spots. Several people told me that the salt from the tires gets into the concrete, causing it to crack.

Can we rough up the concrete floor and then top it off with 3 inches of a smooth concrete base? Will that stick? Should we paint the garage floor or seal it to prevent the salt from getting into the new concrete?

A. The concrete contractor, knowing the problems we have in Vermont with salt on the roads, should have sprayed a sealer on the floor and told you to do it yearly after cleaning it. You can get a clear sealer from a masonry supply house. You can repair the damaged areas with one of the vinyl-reinforced products available in the same stores. Thorocrete and Top-N-Bond are two such products. After five years, it is too late to insist that the contractor come and fix the floor for you under a warranty, but he may be willing to effect the repairs at a reasonable price to make amends for his oversight. Don't paint the concrete; it is likely to peel off. A stain may work.

• Henri de Marne was a remodeling contractor in Washington, D.C., for many years, and is now a consultant. Write to him in care of the Daily Herald, P.O. Box 280, Arlington Heights, IL 60006, or via e-mail at henridemarne@gmavt.net.

© 2009, United Feature Syndicate Inc.