Looking for a 3"x3"x4" or 4"x4"x4" Metal Ductwork Wye

[woodworker2000]

I am re-routing the exhaust for some bathroom exhaust fans in my attic. I am trying to combine two 3" runs into a single 4" pipe to reduce the number of roof penetrations. Does anyone know where I can find a 3"x3"x4" metal ductwork wye in the Raleigh/Wake Forest area? If that size can't be found, I suppose I could use a 4"x4"x4" wye and two 3" to 4" reducers but I would prefer not to have to add the reducers. It doesn't need to be a very heavy gauge of metal but it does need to be metal and not plastic. Any help would be appreciated.

 

[ehpoole]

Just an FYI: Unless both fans are powered on by the same switch, you will likely need some sort of a damper/backflow to prevent one fan from backing up and blowing moist air & dust out the vent of the unpowered fan.

If both fans are powered on by the same switch then a damper probably isn't necessary unless one fan is significanty more powerful than the other.

 

[Travis Porter]

I have seen the 4x4x4 at both Home Depot and Lowes in Wake Forest in the past. In HD in Wake Forest, it is on the aisle with the toilet repair parts but on the opposite side.

 

[woodworker2000]

I'll check both HD and Lowe's again.....looked but didn't see in either place. Could be that I just overlooked it. Thx.

 

[Charles Lent]

Like Ethan (ehpoole) said, that won't be a very good idea, and I think it's a code violation. You will get cross flow if both fans are not on at the same time. I think you'll be very unhappy with the results.

Charley

 

[Skymaster]

2 3" runs into a 4" run is not good. Insufficient capacity. Most likely you will need 6 or 8 maybe to handle that flow.

 

[woodworker2000]

What I intend to do is just replicate what is already there and (presumably) passed code when the house was built. Right now, I have two bathroom exhaust fans (in separate bathrooms) each venting through what I consider to be unreasonably long runs of 3" vinyl flex hose (each fan has its own run of hose). The two 3" runs of hose both terminate at the same point at a single 4" roof exhaust (a hole cut in my roof with a metal cover about 3" above the shingles). Each flex hose just empties into the roof exhaust.

What I intend to do is re-route each exhaust fan run using either rigid metal duct or flexible metal duct. The two 3" runs will join at a wye which will be connected directly to the single 4" roof exhaust.....essentially the same thing that is happening now but without the wye. I really don't think I will get much, if any, backflow from one exhaust fan to another since the exhausted air from one fan, like all things in nature, will take the path of least resistance and exit through the 4" tunnel to through roof 5" away and in the direction of the airflow rather than reverse its course 180 degrees to push back against a 3" "tunnel" of air to flow back through the other exhaust fan (which is probably 15 feet "upstream").

I am still looking for a 3"x3"x4" wye or a 4"x4"x4" wye. I checked HD in Wake Forest and on Capital Blvd with no luck (they had both 6" and 8" wyes but no 4").