Replace main stack, how far down to go

supaphly42

The main stack in the house I just bought is cast, everything leading up to it has been replaced with PVC. I'd like to replace the stack with PVC as well, since I'm adding a basement washer/dryer, and plan to add a sink and toilet as well. I figure since I have to cut it up anyway, replace it all and get rid of all the adapters in there.

It's probably the simplest setup I've ever seen. It's a ranch, stack is right below bathroom. Toilet sits on top, sink appears to run into the vent pipe, and kitchen sink and tub are on a line coming in as well. I'm just wondering how far down I can/should cut the pipe. I don't want to get into tearing out concrete right now, so something above floor level. It has a cleanout right at the floor, should I cut below or leave that and cut right above it? Like I said, I want to add a toilet down there at some point, so I need to be able to Y into it as low as possible. Here are some pics. Any/all help and advice is appreciated!

TheEplumber

For the CW and sink you can cut the stack a few inches above the hub and convert to plastic by using a Pl x ci shielded coupling.
Use a 4x2 tee to run horz. to your new fixture location.
Then vent the new fixtures. Also, that existing stack is extremely heavy so support it well when you chop into it. They're known to come crashing down
If your PVC is right outside, consider breaking the floor out, tunnel under the footing and replacing all the cast.
Also, Is that a toilet flange next to the stack?

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supaphly42

I actually have no idea what that is in the floor next to it. Haven't tried to look down in. There's a cap, but it wasn't screwed on, flipped upside down and just sitting there. That would be handy if it's an old flange. And no clue what's under the floor or out to the road, could all be cast as well.

Thanks for the info. The top chunks are all strapped to the joists, but that one long piece isn't held up by anything. Definitely gonna be a brute.

TarheelTerp

Until you're ready to do the sink and toilet floor work leave the rest alone.
The washer drain can be adapted into the TEE at the bottom of the stack for now.

supaphly42

Hmm, good point. Would certainly make it so we can do laundry much quicker/easier! We've lived here for a week yesterday, and after moving, laundry is piling up pretty good, haha.

Also, here's a close-up of that other drain in the floor and the cap. Does it seem like a flange? And might it still be usable?

VIPlumber

Definitely a toilet flange. Usable? Only a camera pipe inspection can tell for sure.

supaphly42

Gotcha. I'll have to look into that when it's time to add the toilet in and have someone check it out. Would certainly save a lot of work.