Hi There. This should be a fairly simple one. I'm putting a standing shower stall in my basement washroom but don't have rough-in for a shower. The rough-in for the toilet and lavatory are there, however. The lavatory drain is 1 1/2" but turns into 2" about 8" above the concrete. Because I am plumbing above the floor for my shower, i have to put the shower on a raised platform. In order to do this and not have a huge step to deal with, I plan on draining my shower with 1 1/2" ABS pipe, so my vertical space requirement under the shower will be much less than if I used 2". The drain pipe will then travel about 8' into the bottom part of the lavatory drain, which is 2" at the junction. I plan on giving the 1 1/2" drain pipe about 1/4" per foot of slope, so the overall slop should be about 2". My vent for this drain will be about 18" from the shower p-trap, between the shower and the lavatory. I have included a drawing which I hope will help visualize the situation (though the view is from the top). Does this sound/look acceptable?
Hmmm... I can't seem to put the picture in here for some reason... maybe I can email it to someone if this gets looked at..

Looks good to me. The only thing I would change is the 90 coming out of the shower. I would use two 45's or a long sweep to do away with the sharp bend. I would also install a cleanout on the shower line for a little insurance.
Good luck, Tom

Looks good to me. The only thing I would change is the 90 coming out of the shower. I would use two 45's or a long sweep to do away with the sharp bend. I would also install a cleanout on the shower line for a little insurence.
Good luck, Tom

Thanks Tom... That's a very good suggestion considering my decision to go with 1 1/2" drain... I struggled with this a bit and you have definitely set my mind at ease. I have only been a member for 2 days but have reviewed many of your answers about plumbing and they have all been excellent... it's a learning experience. Thanks again.

PGerard, You're probably done by now but a 1 1/2 inch shower is fine especially if you use one of the new lower flow heads. I'm building a shower right now myself.