Many people with two restrooms in close proximity question if they can be vented together. Many will tell you that you won’t be able to do it. There are potential code problems, and a backdraft can push air from one restroom into the other. While all of the above is true, there are ways to do it in a safe and code-compliant manner. Building laws make it illegal to circulate air from one bathroom to another. You must not allow air to circulate through your attic or garage. It needs to be vented outside. The problem is that if you use a Y duct connector to connect two fans, it’s simple for one of them to exhaust air into the other bathroom.

A backdraft damper is a simple solution. These items were designed to protect chilly air from entering your home. Backdraft dampers, on the other hand, can be utilized to prevent air from blowing into the other bathroom. Backdraft dampers are also inexpensive, costing less than $20, and simple to install, requiring only a few screws and a screwdriver. You can allow air to blow out of either bathroom but not back in by attaching two backdraft dampers, one to every side of the Y connector. Another option for venting two bathroom exhaust fans is to use only one fan instead of two.

Ventilation is provided by an inline centrifugal fan, which is positioned inside your ductwork. Backdraft dampers are much more costly and complex to mount than centrifugal fans, but they could also be more useful. Where the 2 ducts of your Y connection join to form one duct, an inline centrifugal fan should be placed. The inline centrifugal fan will be able to take air from bathrooms and exhaust it outdoors this way.