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Bathroom exhaust venting

8363 Views 48 Replies 16 Participants Last post by  Michaeljp86
I have 2 exhaust fans to wire and install.

Can I couple the (2) 4" aluminum vents into 1 common 4" vent?

Or am I better off doing 2 separate runs?
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In theory that would work as long as both fans aren't running at the same time. Each fan will have a flapper to prevent reverse air flow. But if they're both running, neither one will be able to push the air at full efficiency. :no:

Related question: Where are you running the vents to? Roof vent, ridge vent, gable wall? The last is best when practical. And remember not to have any low spots in the run that could collect condensation. :thumbsup:
Can I couple the (2) 4" aluminum vents into 1 common 4" vent?
I've always done separate runs. My thoughts on this are because that little plastic flapper on the fan units aren't very substantial and you dont want a deuce from one bathroom to be evident in adjacent bathrooms.

I would imagine that if there is any air pressure on them at all (from the wrong direction), they would open.

Just my $0,000.02
I've always done separate runs.


I second that. It can be quite a pain though if your in a tight space and sometimes the HO doesn't like the looks of two vents side by side in the soffit or whatever but I've always run 'em separate.
This is why the mechanical contractor should install the fart fans.
I have 2 exhaust fans to wire and install.

Can I couple the (2) 4" aluminum vents into 1 common 4" vent?

Or am I better off doing 2 separate runs?
if your going to run 2 fans on one duct look into http://www.americanaldes.com/products.html they can vent multiple fans on one exhaust point.
I'm a wierdo. Since I'm an electrician, I let the HVAC people do the venting.
Some of us don't have to choose between walking and chewing bubble gum. :laughing::jester:
I'm a wierdo. Since I'm an electrician, I let the HVAC people do the venting.
I agree for new construction or remodeling, but I must admit that for swap outs on service calls, I have run these myself. I usually duplicate the existing setup, unless they just vent into an attic.
This is why the mechanical contractor should install the fart fans.
A) Gable ends (split level home).
B) Because I'd rather not sub out any venting on a small job such as this.
C) Thanks for the link.
D) Chewing gum and walking at the same time is something I learned very early on in life.

I'm going to install 2 separate runs. Seems to make the most sense. There is a very good chance of both fans being on at the same time.
Hopefully I get this job I went looked at today. Complete gut job remodel. I will be more than happy to have an HVAC professional do the venting. :thumbsup:
This is why the mechanical contractor should install the fart fans.
Thanks for the tips regarding condensation build up.
I would just connect the fans to each other and call it a day.
.
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Why even do that?

The HO will never go up in the attic and actually check your work.
Mag - I've put a "y" connector right close to the exterior vent and then connected two runs into that. Kind of a last resort thing if they don't want two vents, etc.

Also, it's usually far enough down the run that backdrafting would not be a problem.

x2 with that Tin said about low spots. Also, think about insulated ducting if it is in an attic area.
I was planning on doing it like I've always done it.... flexible aluminum.

Is that bad (really bad!) because the moisture meets the cold in air in the winter?
Mag - I've put a "y" connector right close to the exterior vent and then connected two runs into that. Kind of a last resort thing if they don't want two vents, etc.

Also, it's usually far enough down the run that backdrafting would not be a problem.

x2 with that Tin said about low spots. Also, think about insulated ducting if it is in an attic area.
I want to do it like a pro.
I'll let an HVAC guy answer - just my opinion, but I do not like flexible aluminum - either ridgid or insulated.
I was planning on doing it like I've always done it.... flexible aluminum.

Is that bad (really bad!) because the moisture meets the cold in air in the winter?
Then do what Zinsco suggested and connect them together...like you pointed out, slim chance the h/o is gonna check. :laughing:
I want to do it like a pro.
I would defenatly install two 4" vents. I wouldn't short cut it. It would probably even take you longer to connect the two tubes together than it would be just to do it right.http://www.eliteroofingwi.com/
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