Bathroom plumbing question

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currently in place is the 4” cast iron stack which has a 3” copper pipe oakumed in and right below it is a 1.5” copper pipe oakumed in. there is also a 1.5” copper pipe oakumed in way above for dry venting the lav.

the 3” and 1.5” are very close together and probably too tight of a space to get ABS pipes into both so i figured I would run everything off the 3” and cap off the 1.5” with a flexible cap to prevent any sewer gasses from coming up through it.

i’ll attach 3” abs to the existing copper that i’ve cut down using a 3” shielded coupler then wye off that to get the toilet drain in for a wall mount toilet. the other end of the wye extends to a section with a 3” to 2” reducing wye. the 3” of this wye will be capped off and the 2” will extend on for the shower drain. the 2” line will have a 2” to 1” reducing wye with the 2” portion going to a p-trap under the shower and the 1” will carry on to the lav where on the vertical it will have a santee installed to branch off for a dry vent.

in this configuration i assume the 1.5” lav pipe will act as a wet vent for the shower and toilet preventing the need to add any further dry venting?

will this all work? any issues?





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Looking at your drawing... venting for the lav is wrong. Looking at your last photo, it seems like an easy-enough change to implement.

Use a sanitary tee, and keep the vent path, that is hooked to the input of the santee ,vertical (within 45 degrees of plumb) until above 6 inches above the flood level of the lavatory.
Hey, wait a minute.

This is awkward, but...

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