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Heating & Air Conditioning

Bath exaust fan/range hood ducting

17 years ago

Hi, We have a bath that bumps up to the kitchen. The bath has a fan. The kitchen has a hood. Both require 6" ducting and will vent out the exterior wall,(apprx. 7'). My question is: can i tie the two together and vent outside with one vent cap? Any thoughts would be greatly appreciated,Mark

Featured Answer

fairyprincess

17 years ago

Sierraeast:

You can use one outside exhaust vent for both of them.

Put a "T" cap with the opposing openings the same size or larger than the opening connecting to the pipe on the outside of the vent tube so that the "T" openings run horizontally.

It will prevent back pressure blowing through the vent and possibly mixing toilet air with kitchen air.

Any air passing through the horizontal "T" fitting will cause a venturi effect (I'm old enough to remember carburetors.) which will actually suck air out of the vent tube.

The lower position of the vent in the bathroom and the position of the range hood relative to the higher placement of the outside exhaust position will form a natural upflow which will be aided by the venturi action of outside air flow across the horizontal "T" cap.

This will work well for outside vent placement but will not work if they both vent to an attic crawl space. You need moving air for the "T" to work right

Forgive Bama Dude, he's a good guy but undertrained by Trane propaganda.

Fairyprincess

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Comments (6)

bama_dude
17 years ago
no,unless you want your food to smell like poop.
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bob_brown
17 years ago
For the amount of time both appliances are used, it would probably work if you use dampners to act as a one way air flow and restricting air from flowing into the opposite area, otherwise like BD said, you will smell poop while cooking.

Local codes may not allow this arangement so check with plumbing inspectors before attempting this venting solution. Personally, I would not want to take a chance that I would smell poop when I was cooking. If you smell poop, food will be contaminated by that time. It will be too late.
fairyprincess
17 years ago
I have installed range hoods and the Broan units I have installed all have a one way gravity drop damper that closes when the hood fan is off.

If you use a "Y" connection from the bathroom and kitchen vents attached to the exhaust pipe going outside, you WILL NOT get a poop smell.

If you are branching the bath and hood connections to the exhaust pipe going out, use an half "Y" or 30 degree connector pointing toward the outside.

Never, never connect both vents in a manner where the openings face each other at their inside connection points or you may have smells going from kitchen to bathroom or bathroom to kitchen.

Yes, connecting them to the same exhaust tube leading outside is against code, but that is a choice you have to make.

Fairyprincess
sierraeast
Original Author
17 years ago
Thanks all for the responses.They are both broan units with draft blockers built in, but they are simple plastic flaps that possibly could fail.I haven't checked code for this in our area, but if it goes against the grain, i better not go in that direction,as this is a new build, and will get inspected.

Im not a total straight shooter when it comes to codes. They are there for a reason,but some have been around long enough where there are more reliable,efficient ways of going about it. What stops you is the code that says "no can do". But in any event,i was basically looking to eliminate one of the vent caps as they will basically be real close together where they protrude through the outside wall.I guess i should play it safe and go with independent ducting/vent caps. Thanks again for the responses and info.
John Michalke
3 years ago
hey sierraeast, I am facing this same configuration. how did you finally resolve it? how did it work out? I really didn't want to punch two holes through the brick on the side of my house, mere inches apart.

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