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I received a call from a couple interested in our handyman services the other day. Looking at their issue, I saw 2 bathrooms where PVC pipe was connected directly to ceiling exhaust fans, and then run straight up through the roof. The run in each case is probably about 12-15'. In cold weather, enough condensation is present to have water dripping from the fans, onto drywall, and onto the floors. Some insulation is present where the fans are, but I don't believe the PVC is insulated in any way. They do have elbows on them above the roof, so nothing is getting in there, except extremely cold air. The fans themselves are not high quality either, so I doubt there's much force pushing the warm moist air through to the roof openings. Any thoughts or proven solutions to this issue would be appreciated. I have not seen PVC used in this application before, and am a little stumped as to the most cost effective solution. The house is also under an agreement of sale, so the owner is interested in fixing this for the new owners, but would obviously like to do so economically.
 

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I received a call from a couple interested in our handyman services the other day. Looking at their issue, I saw 2 bathrooms where PVC pipe was connected directly to ceiling exhaust fans, and then run straight up through the roof. The run in each case is probably about 12-15'. In cold weather, enough condensation is present to have water dripping from the fans, onto drywall, and onto the floors. Some insulation is present where the fans are, but I don't believe the PVC is insulated in any way. They do have elbows on them above the roof, so nothing is getting in there, except extremely cold air. The fans themselves are not high quality either, so I doubt there's much force pushing the warm moist air through to the roof openings. Any thoughts or proven solutions to this issue would be appreciated. I have not seen PVC used in this application before, and am a little stumped as to the most cost effective solution. The house is also under an agreement of sale, so the owner is interested in fixing this for the new owners, but would obviously like to do so economically.
Better install a p-trap. :laughing:
 

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Insulate the pipe or chop it out and replace with insulated flexi.
 

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Kowboy
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Put two 45 degree connectors in the pipe on the way out with a "drip leg" at the bottom of the last one. That way the only condensate that can drip would that which formed between the 45s and that shouldn't be much. I'd still insulate.
 

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I've never seen PVC for that purpose either but can't think of anything wrong with it; just insulate them.
Check the elbows above the roof line. I'm not sure if a PVC elbow byitself is enough to keep out wind driven rain. Come to think about it they should also have a screen and check-valve type flap. Are they flashed properly?
 

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The PVC's part of the problem. A metal duct gets heated above dew point right away, once you start blowing warm air through it. The PVC stays cold long enough to condense some water. Check the check valves, put a proper cap on it. If the pipe's accessible, switch it out for metal.
 

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I have had a six foot run of four inch pvc on my bathroom fan since I built my house in 1998. I have it wrapped with insulation and sloped to the vent which is out my gable wall so any condensation that migh form runs out the vent and not back into the fan.
if I use metal duct on a job I always insulate it
nicko
 
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