Yet another Bath Shower Drain Question

[tp61]

I have a 1978 house that is slab on grade. The hall bath had a typical tub/shower combo, two sinks with separate drains, and a toilet. My goal is to add a shower so I started exploring the existing drain situation. The bathtub had a 1.5 inch trap fitted to a 1.5 inch cast iron drain. The nearest sink has a vent and a 1.5 inch cast iron hub coming up through the slab in the wall. I snaked an inspection camera down the drain pipe and found that it intersects another pipe at about 45 degrees about 4 feet from the tub area toward the main drain line that runs diagonally from the master bath towards the front where it descends to the sewer main. The nearest sink drain appears to angle toward the second sink drain. I am starting to think that the bathtub and both sinks converge to one pipe that leads to main drain line. I don't yet know which way the toilet closet bend goes (other than towards the main drain line).

My question is whether it is likely that when the tub+sink+sink drains converge that they transition into a 2 inch pipe before joining the main drain line.

I can open the slab in this hall bath but dont want to open the slab all the way to the main drain line as that is probably 6+ feet from the second sink drain point and under a finished hall floor.

I do plan to shift the toilet about a foot from the current location and that requires opening the slab there and of course replacing the lead closet bend with pvc. Would it be acceptable to add a wye at this point so that a 2 inch branch can flow into the 3 inch line that is surely under the toilet. That would be about five feet from the desired shower drain point and would all be under the bathroom floor.

This is a lot of info so any guidance would be appreciated.

 

[Breplum]

I'd be very surprised if your closet bend is lead from '78.
no way to say if 2" is available or not.
no comment on your add a 2" branch. I am old school and always want a WC vent before adding branches.

 

[Sponsor]

 

[tp61]

I'd be very surprised if your closet bend is lead from '78.
no way to say if 2" is available or not.
no comment on your add a 2" branch. I am old school and always want a WC vent before adding branches.

I had to replace the closet bend in the master bath as it was lead and failed. I was able to save the one in the powder room bath when I replaced the flooring and toilet in that little bath. So my assumption is that all three closet bends put in when the house was built are the same. I'll lift that toilet this weekend to see which direction it 'bends' towards to see if it heads under the hallway behind the wall the toilet is against or if it heads more toward where the sink drains go. That toilet is vented as I see the vent pipe coming up into the attic right above that toilet. Not sure exactly how that vent is connected into the soil drain. I'll soon find out I think.

 

[tp61]

I had to replace the closet bend in the master bath as it was lead and failed. I was able to save the one in the powder room bath when I replaced the flooring and toilet in that little bath. So my assumption is that all three closet bends put in when the house was built are the same. I'll lift that toilet this weekend to see which direction it 'bends' towards to see if it heads under the hallway behind the wall the toilet is against or if it heads more toward where the sink drains go. That toilet is vented as I see the vent pipe coming up into the attic right above that toilet. Not sure exactly how that vent is connected into the soil drain. I'll soon find out I think.

I opened the slab around the original closet bend and indeed it was 4 inch lead into a 4x2x3 tee that feeds straight down then turns 90 degrees toward the center of the bathroom. I'll replace that lead with PVC to shift the toilet over several inches. All other drains in this bath combine into 2 inch cast pipe and wyes. So one of the sink drains will become a shower drain. Will need to clean up the manifold under the old jacuzzi tub.
One curious thing is the second hot supply line that goes to the tub. Turns out this is the mysterious pipe that comes out at the water heater and seems to be a hot water loop.

 

[Jeff H Young]

the 2 inch should be good for a shower might need to install a vent for it over in a wall and connect to an existing vent.
The pipe under slab not enough detail but could be recirc line. it might now be a dead leg if it goes all the way back to the w/h and is then capped thats undesireable for sanitary reasons germs trapped can multiply