Piggy backing exhaust vents

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Old 09-04-14, 07:13 PM
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Piggy backing exhaust vents

My clothes dryer is located in the basement and is vented outside with 4 inch galvanized duct run approx 20 feet long.
I am building a darkroom (photographic silver print wet darkroom) this winter and would like to piggy back the vent exhausts.

Would there be an issue with installing a wye in the dryer duct run and and adding an exhaust fan from the darkroom so they share the last 8 feet or so of the run?
 
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Old 09-05-14, 09:49 AM
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That would allow the dryer to exhaust into your dark room and vice-versa.
 
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Old 09-05-14, 09:51 PM
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Thank you Mitch,

A while back I looked in to piggy backing the kitchen and the bathroom to save one wall penetration and it came back as not recommended too, I guess I just have to come to terms with one exterior vent per use.

Have a good weekend,
 
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Old 09-06-14, 12:58 AM
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I guess I just have to come to terms with one exterior vent per use.
That is correct. About the only time you can have a single outside vent is when you have multiple bathrooms connected to a single remote exhaust fan and that fan has a single vent.
 
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Old 09-06-14, 03:41 AM
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Even without the dryer heat venting into room, dryer vents also carry a lot of lint which I would not think good for your prints.
 
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Old 09-06-14, 06:03 AM
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dryer vents also carry a lot of lint which I would not think good for your prints.
If a gas dryer dont forget about CO poisoning... ( You can die!!!!!! )
 
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Old 09-06-14, 06:26 AM
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That is correct. About the only time you can have a single outside vent is when you have multiple bathrooms connected to a single remote exhaust fan and that fan has a single vent.
So, if I have back to back bathrooms and want to add a vent fan to the bath that borders an outside wall (hence no vent to begin with) I can't tap into the existing vent pipe in the attic crawl space? It's only water vapor and only draws air out and up. What is the problem?

Next year I plan on remodeling this bath (shower only) and was debating about putting a vent through the wall to the outside or tapping into the vent that is right next to it.
 
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Old 09-06-14, 06:53 AM
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Norm, as Furd mentioned in his post, you need a remote inline fan- to power the suction from both vents. They are also quiet. You don't hear the whirling inside the bathroom.

Remote In-Line Fans - Bath and Ventilation Fans - NuTone
 
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Old 09-06-14, 07:29 PM
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Thanks guys, point is taken.

Furd
That is correct. About the only time you can have a single outside vent is when you have multiple bathrooms connected to a single remote exhaust fan and that fan has a single vent.

pugsl
Even without the dryer heat venting into room, dryer vents also carry a lot of lint which I would not think good for your prints.
Indeed, dust is the ultimate enemy!
 
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Old 09-06-14, 08:04 PM
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So, if I have back to back bathrooms and want to add a vent fan to the bath that borders an outside wall (hence no vent to begin with) I can't tap into the existing vent pipe in the attic crawl space? It's only water vapor and only draws air out and up. What is the problem?
You would need to install backdraft dampers in the discharge duct from each fan as well as increasing the size of the combined discharge duct. The backdraft dampers will add a significant amount of resistance to the outflow of air and this will decrease the volume of air discharged.
 
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