Water heater rarely used in vacation home
Q: My vacation home stays vacant for months at a time. Whenever I return, the hot water has a strong sulfur smell, like rotten eggs. What could be causing this problem, is it unsafe, and how can I keep this from happening?
A: Water heaters contain a specialized metal rod known as a sacrificial anode. Its purpose is to absorb the corrosive effects of water and minerals to prevent deterioration of the water tank. Gradual disintegration of this rod produces small quantities of sulfur and hydrogen gas. When the water heater is subject to daily use, these byproducts pass from the plumbing system without being noticed. When the house is vacant and no water is drawn from the faucets and appliances, the sulfur and hydrogen gradually accumulate, and the sulfur dissolves into the water, causing the rotten egg smell when you return to the property.
The way to eliminate this smell is to drain the water heater tank each time you vacate the property.
The hydrogen gas can actually be a more serious issue than the sulfur because hydrogen is highly combustible. When a water heater is not used for long periods, hydrogen can accumulate at the top of the tank. When released through open faucets it typically dissipates into the air without being noticed. However, if the dishwasher is the first fixture to be operated after a long absence, the appliance could become filled with hydrogen, and a spark from the electronic controls could then cause an explosion. This is not a common occurrence, yet it has been known to happen. For this reason, draining your water heater is doubly recommended.
Q: I've discovered a lot of moisture and humidity in the crawl space under my home. The insulation has become saturated with condensation, causing some of it to fall down, and mold appears to be growing on the wood framing. What can I do to correct these conditions?
A: Condensation under a house usually indicates insufficient ventilation. The building code requires that crawl spaces 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. In homes with excessive ground moisture, additional ventilation may be needed.
If the subfloor insulation is saturated with moisture, the insulation may have been installed upside-down. Therefore, make sure the vapor membrane is not on the downward side. That is a common cause of moisture condensation that can lead to fungus damage to the subfloor structure and possible mold growth.
Corrective steps should include making sure the grounds are sloped away from the building to promote proper drainage, making sure the subarea has sufficient ventilation, and having the wood framing professionally inspected to determine the extent of damage. The insulation should be removed to enable a thorough evaluation by a licensed pest control operator, and mold testing is advised to ensure against any health-related risks.
• To write to Barry Stone, visit him online at www.housedetective.com.
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