Installing washer including line

I want to install a washer and need help with the drain.

I currently have two vertical 2" pipes (black pipe) running through the house, but only one vents through the roof. I assume the other connects to the first in the attic (haven't checked though). The one through the roof has a 2nd floor kitchen sink attached to it via horizontal drain with P trap as shown on diagram. The one that connects in the attic (I assume) has a 1st floor horizontal drain with P trap as shown on diagram.

Both pipes continue into the basement and turn horizontal with cleanouts as shown in diagram, connect to eachother and then finally connect to a 4" drain pipe that is leaving the house to sewer.

I have two options as I see it, the first involves tearing out a lot more plaster and lathe, finding the 1st floor vertical drain in the exterior wall, and cutting through some studs with a 2" diameter pipe and P trap to connect to that vertical drain.

The second I like better, but am not sure if it is correctly "vented" or allowed. It involves dropping a 2" drain pipe from the washer into the basement and tieing in to the existing "1st floor kitchen sink" pipe at the cleanout, providing a new clean out afterwards, as shown in 2nd diagram.

Whatever I do, I need to replace the "1st floor kitchen sink" pipe in the basement at the horizontal run, because it's leaking. I was considering replacing all of the 2" black pipe in the basement because it all looks pretty bad along the horizontal runs. View attachment option 1.pdf View attachment option 2.pdf

Ok,

So here is what I've learned so far. Correct me if I'm wrong.

You can't wet vent a fixture into a waste stack of another fixture unless they are on the same floor. This removes the option of tieing into the 2nd floor kitchen stack that is one stud over from the new washer I'm installing.

You can wet vent a fixture into a waste stack when they're on the same floor, but wet vent part must be one size larger than minimum required. The CI pipe for the first floor kitchen sink is 2" diameter.

Is the current 2" diameter the correct sizing for for a washing machine and kitchen sink? The Washing machine would tie into the 2" pipe above the sink. Do I need to replace with larger pipe from the washer down?

Thanks for the advice.

ièm not familiar with your local code, ours allows multi-story wet venting, providing all requirements are met. Best recommendation I can give is call in a professional.

Most codes don't allow wet venting the sink over a washer.
They like to see them each vented

UPC as I read it only allows wet venting ..."bathroom groups on the same floor"

Love the picture Terry. Really helps. I'll make sure to add a separate vent line that connects above the sink as shown. I'll take pictures tomorrow before sealing it up to make sure i didn't miss anything.