Route new bathroom vent duct to existing bathroom vent duct

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Old 01-26-09, 05:20 AM
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Route new bathroom vent duct to existing bathroom vent duct

Is it possible to vent a new bathroom fan into the duct of an existing bathroom fan using a "Y" connector? I want to install a bathroom vent fan into our master bath which doesn't have one. Instead of having to make another opening on the house exterior, I'd like to just tie it in to the existing ventillation duct work of the adjacent bathroom. I have attic access above both bathrooms.

Are there any foreseeable problems with this? Do they even make a "Y" connector in 3 in. diameter?
 
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Old 01-26-09, 12:14 PM
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Route new bathroom vent duct to existing bathroom vent duct

I'm not an expert but I wouldnt do it. Running one fan and not the other could force moisture / oders into the other bathroom depedning on how the vent duct is laid out and where you cut it. But if you run both at the same time neither will perform very well - bathroom fans are pretty low power devices and they will be fighting each other for the solo outlet duct. Code violation anyway.
 
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Old 01-26-09, 12:18 PM
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There is usually a baffle that acts as a one-way valve on both fans that keep air from returning to the fan from the outside. I wonder if the "Y" connector, if they make one, has baffles on the 2 ends.
 
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Old 01-26-09, 12:31 PM
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I guess my point was that those baffles are not really airtight - they are more like flaps. They wont perform under negative pressure, they arent deisgned to. Wind never pressurises those little ducts the same way. But I bet if you pressurize that duct with a powered device there will be a lot more oder / moisture than you imagine. I dont know of any Y pipes (really a T pipe) with flow directors on them. Someone else might. BTW, I have this same challenge - one bathroom is dumping inefficeintly (to a blocked soffit vent). I considered cutting into another duct run and was told all of this: both fans will fight each other more than I think, one fan will push oder / moisture into the opposing bathroom more than I think, it would have to be changed if we sold the house (it's not code), and it's the same amount of Mickey Mousing to do something custom like this vs. doing it the right way. So I just bit the bullet and it works very nice.
 
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Old 01-26-09, 12:36 PM
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Thanks for the additional info. All good points. I think I might have to do what you did.
 
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