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Water dripping from furnace flue pipe

Q. We purchased a home that was built in the 1960s. The forced air furnace is new, but the metal flue pipe from the furnace is connected to the original concrete flue pipe that extends up through the roof. Whenever the furnace is turned on, water drips from the flue pipe onto the top of the furnace. The contractor who installed the furnace said that this is not a safety problem and won't damage the furnace. We checked with another heating contractor, and he said the same thing. But this doesn't seem right to us. What do you think?

A. What you are describing is more of a nuisance than a significant defect. Basically, here is what's happening: Combustion exhaust in a furnace consists primarily of carbon dioxide and water vapor. During the first few minutes of operation, the flue pipe is cold, which causes the water vapor to condense on the inside of the flue and flow down until it drips onto the furnace. If the flue pipe was made entirely of metal, this would probably not be happening because a metal flue warms up quickly. However, the old concrete pipe (known as "transite") takes longer to become warm and therefore promotes condensation and dripping.

If you have the transite pipe replaced with an all metal flue, that will probably reduce or eliminate the dripping. However, be aware that transite contains asbestos and should be handled by a knowledgeable professional, in accordance with EPA environmental safety standards.

Q. I am purchasing a home that is currently being built. The builder has just started installing the drywall, and I've noticed that some of the panels in the garage are 5/8-inch type X, while others are just standard ½-inch drywall. Isn't type X drywall required for fire safety in a garage?

A. A one-hour fire separation is required on walls and ceilings that separate a garage from living space in a home. That would be where 5/8-inch type X drywall is required. However, in municipalities that use the International Residential Code (IRC), this is no longer mandatory. Why this code was downgraded is a challenge to common sense. To determine what the current requirement is in your locale, contact your local building official and ask that your inspector make sure your new garage complies with this standard. If fire-rated drywall is not required, ask your builder for a quote on upgrading the walls in your new garage.

Q. I am a handyman and I would like to know if an 18-inch platform is necessary for the installation of an electric water heater. Some home inspectors say yea and some say nay. What say you?

A. According to the plumbing code, a platform is required if the water heater is capable of producing a flame or a spark. Since an electric water heater is capable of producing a spark, a raised platform is required. However, this requirement only applies when a water heater is installed in a garage.

• To write to Barry Stone, visit him on the web at www.housedetective.com, or write AMG, 1776 Jami Lee Court, Suite 218, San Luis Obispo, CA 94301.

© 2015, Action Coast Publishing

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