Condensation issue in water heater closet?

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pacumming

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Plumbing/water heater- spots recently on ceiling downstairs, 2 story house. Condensation??? New water heater.

Live in Cardinal Woods now for 20 years but could happen anywhere. Got a new water heater in September on 2nd floor in a tiny closet. In that closet is a metal aluminum vent and also a white stack vent(?) that goes down to 1st floor and also up into attic and through roof. Noticed 1 month after new water heater a small spot on Living Room ceiling. Drywall was fairly dry. Put bleach on it, gone. Happened a few weeks later-bleach, gone. Hmmmm. Could there be a leak? Did not find one anywhere in other bathrooms and that area with water heater. Could white round plastic stack vent in attic be leaking from roof when it rained--Very dry. Wrapped newspaper around it-3 weeks later still dry. Ok, is there any water in closet(2nd floor) where water heater (on floor, pipes, walls)? Nope. BUT in closet is a hole where you can see a large white round PVC stack vent, it has a plug that screws out for clean out. Opened it up. Poured water down in it--water flowed fine, no stain on ceiling below. Double Hmm. Now thinking it could be a decent amount of CONDENSATION forming in the water heater closet on the white stack vent pipe since it is next to water heater in HEATED house and vents to COLD outside (hot and cold air mixing) Put paper towels around stack vent... Waited overnight-- decent amount of water on towels had been absorbed.. So stack vent condensation may be it.
The question is perhaps the new water heater (even though slightly lower BTU than prior one) not as insulated as well as prior one, perhaps strange weather, more condensation ? How solve-will weather as it gets colder solve it? Wrapping blanket around water heater may or may not not make a difference since vent is still in house where it is warm and exits outside roof.... Don't know. Could ripping out a little drywall in closet and wrapping the vent and pushing some sort of round wrapping down and up stack vent help? But may not be possible since vent may also be strapped to wood some where or some impediment.
Interesting that the only variable is the new water heater and perhaps weather. But in 20 years never had a spot on ceiling....
Thoughts? , Thank you Peter
 

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Sparky617

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Natural gas can put out a fair amount of moisture when burned. I'd be curious if your exhaust vent is clear. You might try putting a CO monitor in the closet to see if you've got venting issues.
 

Guzzle

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Plumbing/water heater- spots recently on ceiling downstairs, 2 story house. Condensation???

Put paper towels around stack vent... Waited overnight-- decent amount of water on towels had been absorbed.. So stack vent condensation may be it.
Cold pipe, humid room.
If you can check the temperature and humidity then the dew point can be found.

Cold enough with enough humidity and you would have ice on the pipe.
 

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