Moving 3" vent pipe

[mtn_plumb]

Remodeling a home in the mountains and am at wits end with local plumbers. We've been quoted all over the place... $1,500 all the way to $4,000. I was ready to pay the 1.5k guy, but now he is too busy... and the middle guy said it would still be $2800 without moving any of the supply. There are only a handful of plumbers in the area, making things difficult.

Talking with a plummer in a different city, he said I should do it myself, but I want to get some more feedback before I tear into it.

I have a 3" stack coming up in the middle of the kitchen. Its soil stack from down below. My goal is to move the vent into the wall and add a kitchen sink drain.

Would it be okay to chop the vent up into two 1-1/2" vent pipes and combine those two in the ceiling before exiting the roof?

I created this diagram to help. My worry is that I won't be able to squeeze a 3" vent pipe in the wall.

 

[hj]

1. It takes FOUR 1 1/2" pipes to equal a 3" one.
2. You cannot just install a tee in a vent pipe to connect a sink.

 

[Sponsor]

 

[mtn_plumb]

1. It takes FOUR 1 1/2" pipes to equal a 3" one.
2. You cannot just install a tee in a vent pipe to connect a sink.

How about two 2" pipes?

The 3" pipe coming up through the floor was serving as a drain for the old kitchen as well as a bathroom. That help?

 

[Reach4]

I suspect you need don't more than a single 2 inch vent pipe for that area if there are other vents for the house. I could be wrong. I am not a plumber.

 

[mtn_plumb]

I suspect you need don't more than a single 2 inch vent pipe for that area if there are other vents for the house. I could be wrong. I am not a plumber.

Its the only vent pipe that pops through the roof... and if I have read codes correctly, a soil stack needs to be 3" (or match) if there are no other vents popping through.

 

[Reach4]

I think CO uses IPC. https://codes.iccsafe.org/public/document/code/550/9795976 see table 906.1

Expanding before you go through the roof helps prevent that from clogging with ice.