I'm working on a remodel of my older home. Cast iron piping was used for the drains and galvanized for venting.

The garage was converted in to a bedroom and they built a 1-1/2 bathroom. Now for the fun part, since it was a garage it has cement slab
they laid the original 4" cast iron drain on the cement slab and built a floor over the top of it. So you have a step up into the bathroom. The 4" drain runs to to main line under the home I have a crawl space.

I want to remove that step up, I know I will have to bust up some cement, but only about six feet of it.

This bathroom has always had sewer gas smell on and off, I was thinking maybe the shower did not have a trap. So I was anxious to get the floor wooden floor removed and take a look at the plumbing.

Here is what I found, working from the main line under the home, horizontal y fitting 4x2x4 to a trap to the shower drain, 4x2x4 hor. Y fitting at a 45 angle up to the lavatory drain tee and up to a 2" inch vent it looks like the 45 angle was used to reach to the side wall were the lav and vent were located, next in line was a 4x2x4 hor. y fitting also laying at a 45 angle up also tying into the same 2'' vent, and finally the closet bent and the toliet, so all were draining into the same four inch to the main under the home, and all vented by that 2", does this sound correct? Was this o.k.

Sorry, kind of wordy but trying to give a good picture.
I want to bury my new drain and change location of the toilet,lav and bath
Does the toilet need it's own drain and vent, or can I keep it combined and is that one 2" vent adequate for all three fixtures.

The old set-up everything ran parrell to the main so they just tapped as needed,
My new plan the fixtures would run all on the same wall at right angle to the 4" my only hang up is the shower is left of closet elbow and lav. Is right of closet elbow I wanted to share my shower and lav to share the same drain and vent. Or would it be better to just 4" to closet elbow vent up were it passes thre wall, tee to the right from the same 4" run to lav drain, tie vent with closet, for shower drain tee left from same 4" and also share vent with other fixtures. hope I explained it o.k.

Sorry for the delay in aswering.

Unless you ploan on running a separate vent for the shower you'll reconfigure the shower so it can connect with the lavatory drain and be wet vented by it as it was in the original set up.

"Or would it be better to just 4" to closet elbow vent up were it passes thre wall, tee to the right from the same 4" run to lav drain, tie vent with closet, for shower drain tee left from same 4" and also share vent with other fixtures. "

Could you make a rough drawintg showing me what youy mean? Thanks, Tom

Thanks for answering Speedball,

I have to apolizgize for my description it even confused me after I re-read it,

Trying to locate a scanner for a rough drawing, In the mean time Let me try again to explain.

Will re-use the 4'' cast, couple to 4'" pvc using adapters you have recomended. Will pass under 2x6 wall (all fixtures will be on this wall)
tee up in this wall for a 3" vent then directly on to the closet elbow 12" off wall.

I wanted the tub to east of toliet and the lavatory to the west.
For the lavatory I wanted to y-off before I went under wall so it will be ahead of the 3" vent, then I would tie the lavatory vent into the 3-vent in the attic. I was hoping to do the same for the bath to the west of the toilet also
y-in into the 4" before It passed thru the wall, but then I realilzed since I have to account for my p-trao my vent would comming out in the middle of the floor on the way to the attic, I dont think the boss would like that. Can the tub be wet vented from the lav vent in this configuration since I have vented the toliet with its own 3"?

I really appriceate your help on this!!

Tom,

Been busy with the day job, tried to do a rough sketch.

Been reading previous posts on your site, maybe it will sink into my brain. When I think I might have it figured out, I get confused again.

Does my plan even look like It may work.?

How about the venting for the shower ?

Don't know where we would be without you TOM

Hope this helps.

Thanks for the reply Growler,

Looks like I am somewhat on track,
My problem is the bathtub vent, would not my shower be vented by the lav vent or the vent downstream of the toilet or would that vent be considered the vent for the toilet.

If I have to put a separate vent for the bath drain what would be the best way to route that? My bath P-trap would be very close to the 4" drain, and I want to have that vent in the 2X6 wall,

Is it possible to combo up with 2x2x2 and then double 90' (since this is only a vent) under the floor grade back to the wall?

Or is it possible to put my P-trap at a right angle to the tub, just not sure if there is enough room to go up with the vent?

Thanks in advance.

"My problem is the bathtub vent, would not my shower be vented by the lav vent or the vent downstream of the toilet or would that vent be considered the vent for the toliet."

Look at your drawing again. You are discharging a major fixture past a unvented minor one and that's a no-no.

" Is it possible to combo up with 2x2x2 and then double 90' (since this is only a vent) under the floor grade back to the wall?"
Yes, just remember to add slope back to the drain line.

"Or is it possible to put my P-trap at a right angle to the tub, just not sure if there is enough room to go up with the vent?"

The "P" trap may be turned in anydirection as long as it sets under the tub wastes tail piece.
Growler gave you good advice. Follow it.
Good luck, Tom