A previous owner developed the attic in our house in 1994. This included adding a bathroom up there (clawfoot tub, lav, toilet).
We want to replace the tub with a custom shower (center drain). The clawfoot tub is alongside an exterior wall (which makes venting tricky).
I've been reading lots about this and was hoping to get a final opinion from you folks before I pull a permit.
Here is a layout of the current DWV plumbing layout for that bathroom:
1) If I move the Bathtub drain 25" to make it a center drain for a shower, I know I should make it 2" pipe (rather than the current 1-1/2"). Can I continue to use the Lav as a wet vent if I run this 2" pipe parallel to the existing 1-1/2" and tie-in via a Wye 18" downstream of where it currently connects? Or do I need to figure out how to separately vent this drain arm?
2) The toilet clogs *much* easier than the identical model in our other bathroom (both are Toto Ultramax's). Would changing the 90 under the closet flange to a long-sweep 90 (from what appears to currently be a vent 90) improve things? If so, would the loss of headroom/slope be a problem? (Currently the 3" waste is 60" long in a 2x10 joist bay, so currently a 7" drop over 60")
3) Currently when you drain the bathtub, it drains in a hurry (!). Problem is, it also sucks about 1" of water out of the toilet bowl. Do I need to install a separate vent upstream of where the 2" Lav/Shower line joins the WC line? If so, can the vent be a horizontally-installed wye? (very little headroom)
4) There are a whole bunch of 45s (four of them) plus a long-sweep 90 as the 3" pipe winds its way through the joist cavities before it finally heads down to the basement. Do I need a relief vent here? Or is 3" pipe big enough to self-vent?
Really appreciate any help you could offer
1) Yes ... continue to use the Lav as a wet vent ...
2) I don't know what to do here
3) No ...Do I need to install a separate vent upstream of where the 2" Lav/Shower line joins the WC line? ...
4) No ...Do I need a relief vent here? ...
Based on what (I think) plumbing code is in BC.