Dear Barry,

My vacation home sits vacant for several months at a time. When I return, the water always has a strong sulfur smell, like rotten eggs. What could be causing this problem? Is it unsafe, and how can I keep it from happening? – Patrice

Dear Patrice,

Water heaters contain a specialized metal rod known as a sacrificial anode. Its purpose is to absorb the corrosive effects of the water and minerals, and thereby prevent deterioration of the water tank. Gradual deterioration of this rod produces small quantities of sulfur and hydrogen gases. When the water heater is subject to daily use, these gases pass from the plumbing system without being noticed. When the house is vacant and no water is drawn from the tank, the sulfur and hydrogen gradually accumulate. The sulfur dissolves in the water, causing the rotten egg smell you notice when returning to the property. The way to eliminate this smell is to drain the tank, by way of a hose, to the exterior yard.

The hydrogen gas, however, is a more serious consideration because it is highly combustible. Hydrogen accumulates at the top of the water heater tank. When released through open faucets it can ignite or explode if exposed to a flame or spark. For example, if the dishwasher is the first fixture to be operated after a long absence from the property, the fixture can become filled with hydrogen, and a spark from the electronic controls can then cause the appliance to blow up. For this reason, draining your water heater to the exterior is doubly recommended.

To prevent the formation of gases in your water heater, the plumbing system can be winterized during prolonged absences. This would entail opening all faucets, turning off the main water supply valve to the building, and draining the water heater.

Dear Barry,

I’ve discovered a lot of moisture and humidity in the crawlspace under my home. The insulation is saturated with condensation, causing it to fall down in places, and mold appears to be growing on the wood framing. What can I do to correct these conditions? – Ken

Dear Ken,

Condensation in the sub-area beneath a house usually indicates insufficient ventilation. The building code requires that crawlspaces be cross-ventilated and that the combined area of total vent openings be at least one square foot for each 150 square feet of floor area. This, however, is a minimum requirement and is not sufficient in all cases. When vents are not provided or when they are blocked by insulation, or if the vapor membrane on the insulation is on the downward side rather than against the sub-floor, moisture condensation can occur. The result can be mold, as you have apparently noticed, or fungus, resulting in dry rot to the floor structure.

The primary issues at this point are two-fold: to eliminate the moisture problem itself and to evaluate and correct any resultant moisture-induced problems, such as mold, fungus, or dry rot damage.

First on the agenda is to remove all of the floor insulation. This will enable a thorough evaluation of the wood framing and sub-floor sheathing by a licensed pest control operator. Mold testing would also be advisable to ensure against any health related risks associated with mold.

And finally, be sure that the sub-area is thoroughly ventilated, at least in accordance with minimum building code standards.

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


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