Replacement of Cast Iron in Tight Space

[AndrewME]

What is the best way to deal with the situation in the photo attached? I'm replacing the 4" cast iron with 4" PVC. The problem is these pipes are near the bottom of the basement stairs so we need headroom as well as space around the stairs when we need to bring items in/out of the basement like a water heater.

Additionally, the drain is directly against an interior foundation wall. It appears that the original cast iron used a sanitary tee in the horizontal direction, which I know I cannot do and keep it up to modern code. I tried to see if a 4"comb wye would fit where the sanitary tee was, but when I lined it up the wall was in the way.

On the picture below, the far left is the stack that serves a upstairs bathrooms, the middle is the first floor toilet.

 

[Jeff H Young]

Description is not making sense. Bottom picture not showing much, top pic . so you're saying the santee on back is going up for a w/c ? no vent?
Put a wye against wall and bring 2 separate lines through hole in floor , it will take a few more fittings

 

[Sponsor]

 

[AndrewME]

The top picture is the best that I have for now. The second picture was just to show how tight it was with the wall and stairs.

Yes, sanitary tee on it's back is to the water closet. The only vent in the house is up the stack that is the 90 going up on the far left.

I was also thinking I'd be stuck using a wye there, but it would decrease headroom compared to now, but it may the the only good way. Would that reduce the venting compared to the current setup?

I also thought about just replacing the stack above the basement level and just deal with the cast iron in the basement once it starts leaking, but that seems like a time bomb.

 

[Terry]

The vent for the toilet can be on a wye below the toilet and run separately. As it is now, dropping a toilet into a santee on it's back it not a good thing. Better to drop into a 90 and bring the vent up by itself.
If you cut anything, be aware that cast is very heavy and it wants to drop down quickly. Before anything gets cut, it needs to be supported well. Especially the vent going up to the next floor. Are you sure that's just a vent and not the waste for a floor above?

 

[AndrewME]

Thanks. Currently, the 4 inch pipe on the left is both the vent all the way to the roof and serves as a drain for the upstairs bathroom.

 

[Jeff H Young]

upstairs drain . I wonder if that work was legal 80 years ago/ Terry sketched What I was thinking but w/c needs a vent perhaps the 2 inch can be vent for w/c. If You got walls open or are doing work makes sence to rework it and do it right /or a little less wr that 2 inch line probebly picks up a lav with vent going to second floor and tie into the stack then out roof

 

[Mr tee]

The rubber coupling where the CI connects to PVC should be a CI X PLASTIC shielded coupling.