QDEAR BARRY: I bought my house more than three years ago and I have had seasonal problems with wet ceilings ever since. After I replaced the roof and gutter system, I learned that the problem was condensation caused by groundwater seepage into the heating ducts below the slab floor. Shouldn't my home inspector have known this would be a problem, and shouldn't the seller have disclosed the ceiling moisture? -- Mark

ADEAR MARK: In homes built during the 1950s and 1960s, forced-air heating ducts were sometimes installed beneath concrete slab floors. This practice was abandoned because of moisture problems. Experienced home inspectors are aware of this and know that forced-air ducts under a slab are exposed to ground moisture and water intrusion. Although home inspectors cannot fully determine the conditions that exist within a duct system, disclosure of common problems involving a buried duct system should be expected.

The consequences of buried ducts go beyond the moisture problems you have experienced. Other concerns include rust damage to the ducts and mold on the interior duct surfaces. Mold in an air duct system poses a health threat because the heating system can convey airborne mold spores. I recommend that you replace your air duct system. You should also have a mold survey of your home.

DEAR BARRY: Why does the water in our upstairs toilet bowl slosh back and forth, even when the toilet has not been used? Our home is only three years old, and the toilet has been doing this since the place was new. Is something wrong with our plumbing? -- Alex

DEAR ALEX: In some places, the plumbing code allows several drains to be vented through a single vent pipe.

If someone runs water at one fixture, this can create a vacuum in the system that can cause water movement at some toilets. In some cases, it can also create draining problems at sinks. Fixing this would require a considerable amount of costly and intrusive work. Because the effects are typically minor, such repairs are usually unjustified.

DEAR BARRY: I have some questions regarding the temperature-pressure relief valve on my water heater. How can I tell if it has been activated? Does it reset by itself? Can I reset it manually? And should it be tested? -- Buzz

DEAR BUZZ: Temperature-pressure release valves are installed on water heaters to prevent the tanks from exploding if the fixture overheats. The valve is held in the closed position by a spring. When the pressure or temperature in the tank causes the valve to open, hot water is released from the system.

If the valve is working properly, it will reseal by itself when the temperature or pressure returns to normal. Most valves, however, never fully reseal because of corrosion or mineral deposits. If that happens, the valve should be replaced.

Testing the valves is not recommended because they tend to leak afterward.

Barry Stone is a professional home inspector. If you have questions or comments, contact him through his Web site, www.housedetective.com, or send mail to 1776 Jami Lee Ct., Suite 218, San Luis Obispo, Calif. 93401.

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