Can you combine smaller pipes on a vent branch to reach the min. 1 1/4" size?

[M Kehoe]

I have an 1890s house. The bathroom that we are redoing had no venting at all for the shower or sink. The only possible route that I have to run a vent to the main vent stack is too narrow to fit a 1 1/4" pipe. But, I can get multiple smaller pipes through the space. Can I combine them in such a way as to meet the 1 1/4" minimum size through that narrow space, and then go back to a larger pipe, before tying the larger pipe into the stack? Thanks.

 

[JohnjH2o1]

Short answer NO

 

[Sponsor]

 

[M Kehoe]

As I was sitting here thinking about your answer, it occurred to me that there actually is another way that I can get the larger pipe where it needs to go. So, thanks!