Hello,
I want to install a bathroom in the Attic.
Can I stack vent this bathroom too?
Thanks.

Hello,
I want to install a bathroom in the Attic.
Can I stack vent this bathroom too?
Thanks.
If you're asking if you can simply connect to the existing vent that runs through the attic the answer's NO.
To avoid trashing the vent of the bathroom below you would have to either install a dedicated vent from the bath below and tie it back in the attic at least 6" over the attics lavatory flood rim or you could run the attic 3" discharge line down to the bath below and tie back to the stack vent 6" under the below baths connection. You may then tie the attic vent back to the existing roof vent. That's the way it's done. Good luck, tom