QI replaced the flapper valve in a toilet in our four-year-old house, but it appears to be leaking again. I can't find any hard-water deposits on the flapper that would impair the seal, but I'd rather not have to keep replacing it. Any suggestions?

AThe flapper valve, at the bottom of the tank and attached to the flush handle by a chain, can be replaced in a few minutes at a cost of only a few dollars. If the valve is leaking, however, thousands of gallons of water can be wasted over time.

If your tank is leaking, there are a couple of things you can do before buying a new flapper at a home center or hardware store.

You don't mention cleaning the valve seat -- the rim of the circular opening in the base of the toilet tank where the tank's water pours through when the flapper valve is open. The valve seat can become rough with mineral deposits from the water or even from dirt that has stuck to it. To clean it, turn off the water to the toilet tank and flush the toilet, which will empty the tank. Rub the seat with a wad of fine steel wool, using a circular motion. When it is clean, the seat should feel perfectly smooth to the touch.

While you have the tank lid off, check to make sure the flapper valve closes completely when you release the flush handle. If the chain that attaches it to the flush handle is too short, the valve won't close. It is usually easy to adjust the chain by removing the clip that holds it to the flush handle's rod and moving the clip up a few links on the chain.

If you suspect a toilet is leaking water between flushes, there is a time-honored way to check: Put a little food dye in the tank when it is full. Do not flush the tank for several hours. If the colored dye shows up in the toilet bowl, there is a leak.

How often do I need to get my chimney cleaned? We have one fireplace and a gas furnace. What time of year should it be done? Also, we have lived in this house for two years and haven't had the air ducts cleaned. Should we have the ducts cleaned?

The chimney should be visually inspected annually to make sure there are no blockages or other dangerous conditions, such as a buildup of creosote from burning wood. The inspection can sometimes be done during the recommended annual furnace cleaning. Some chimneys can be inspected by removing the clean-out plate near the base of the chimney and using a mirror to get an internal view. If there are any signs of problems, a more thorough check and cleaning can be done by a chimney sweep.

Air ducts are seldom cleaned frequently because of the expense (often $500 or more). According to the National Air Duct Cleaners Association, intervals of four to eight years between cleanings are not unusual. Some duct-cleaning contractors will give free evaluations, or you can remove several registers and use a mirror and flashlight to get an interior view. If there are significant deposits of mold and debris, cleaning is probably a good idea.

Other conditions that might warrant duct cleaning: people in the house who have symptoms of respiratory ailments or allergies, and pets or smokers in the house.

The best time to do cleaning of this type is during the off-season, when the equipment is not in use.

My fireplace mantle is painted with a high-gloss white paint. The gas fireplace puts out quite a lot of heat and some parts of the mantel have turned brown, apparently from the heat. Do you know of a heat-resistant paint that won't change color?

Heat-resistant paint is available at most home centers and paint stores, but the colors are usually limited. Silver and black are the most common colors. Automotive stores sell some additional colors, generally darker tones, but there is not a wide choice.

I think your best bet is to choose a regular latex-based enamel, but in a darker tone, avoiding such light tones as white and yellow. Also, I'd be wary of a possible fire hazard. If this fireplace generates enough heat to discolor paint on the mantle, some caution is in order.

Questions and comments should be sent to Gene Austin, 1730 Blue Bell Pike, Blue Bell, Pa. 19422. Send e-mail to doit861@aol.com. Questions cannot be answered personally.