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Moisture around basement wall where gas furnace and hot water heater vent into chimney.

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Our home is a 1960 brick construction ranch in Northern KY.  My hot water heater and furnace (both gas) vent into a single flue chimney.  We get what I believe to be condensation seaping where the pvc and aluminum vent route through the wall.  The furnace pvc seems to extend beyond the top of the chimney by at least 6 inches.  The hot water heater does not have a vent that extends beyond the chimney.  What are the risks involved with this as well as possible solutions?
asked in House Chimney by rikster284 (120 points)
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1 Answer

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Hi Rickster284,
I would suggest calling a professional (heating or chimney sweep) who can check the interior of your chimney and correct all problems. I can’t give you much based on the information provided, just some basic info:
  • PVC vent pipes should not be inserted into the chimney flue if it is still used for other appliances venting. This may be possible with two completely isolated flues but it would need professional evaluation and approval from your local code enforcement authorities.  Check here - furnace and water heater vent
  • Natural draft water heater (if this is what you have) should not be vented using aluminum connectors - click the following link - water heater vent
  • You chimney flue might be too large for venting of an orphaned water heater and require a new, smaller diameter liner. Some basic information covering flue size calculations is here - chimney flue size - but you'd need to use Gama venting tables to get exact numbers.
For more information about venting go to this post - masonry chimney
Just click "comment" below if you have additional questions.
answered by darekrudy (21,730 points)