Dear Barry,

Our water heater and forced-air furnace are both installed on the same raised platform in our garage. Recently, the water heater began leaking and had to be replaced. Our main concern, however, involves the water that leaked into the platform and the adjacent wall. The enclosed space below the platform is part of the duct system for the furnace, and we’re worried about the long-term effects of this moisture. It seems strange that the joint use of the platform would ever have been allowed, considering the potential for mold and other moisture-related problems. Is it OK merely to repair the leak, or should the platform be opened up to promote more thorough drying? –Lisa

Dear Lisa,

Water heaters and forced-air furnaces are commonly installed side-by-side on raised platforms in garages. The potential for moisture-related problems should be obvious when these installations are made, but in most cases, little or no thought is given to the inevitability of eventual water heater leakage. The obvious solution is so simple and inexpensive that one can only wonder why it is seldom practiced. All that is needed is an overflow pan (commonly known as a “Smitty pan”) installed under the water heater, with a drainpipe to convey water from the pan to the exterior of the building or at least to the garage floor.

In most cases, the raised platform serves as a passageway, known as a plenum, for the air that re-circulates from the house to the furnace. If the interior of the plenum becomes wet, mold or fungus can develop, and this can adversely affect air quality within the home. Therefore, immediate steps should be taken to promote rapid drying of the platform as soon as water leakage occurs. To do this, the furnace blower should be operated, along with additional fans in the garage. For professional assistance, there are companies that specialize in moisture removal and water damage mitigation.

Once the plenum has been dried, an inspection of its interior by a qualified mold specialist would be a wise precaution.

Dear Barry,

Our fireplace is equipped with natural gas to help ignite the logs. Is there any requirement to keep the damper open in case of a gas leak? –Nicole

Dear Nicole,

Dampers must be fastened in the open position when fireplaces are set up with gas-log systems (that is, cement logs). With wood-burning fireplaces, this requirement does not apply. The reason for securing the damper is not to protect against gas leakage, but to prevent combustion exhaust from venting into the house. Natural gas has a commonly recognized odor. Occupants would typically notice gas leakage from a log lighter. Exhaust from burnt gas, on the other hand, can go undetected and therefore constitutes a more significant hazard, especially because exhaust from gas logs may contain carbon monoxide.

In older homes, gas logs may have been installed prior to the requirement to secure or remove the damper. In those cases, a special clamp can be added to the damper as a safety upgrade.

To write to Barry Stone, please visit him on the Web at


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