I'm considering adding a 2nd bath to a house that was built in 1951. The cast iron waste stack is in an easily accessible location, but the only vertical space available is below 3 other elbow & just above the lowest why used for clean out. What's the approach for tying into this location? Do I need to lift the upper 3 junctions & pull out the straight piece, cut it, and splice in a new elbow & then lower the 3 connections back down? Or... would I need to pull the upper 3 joints apart & rebuild... or maybe hire a plumber? Also, I'm assuming I cannot tie an entire new bathroom into an existing drain run? Guidance appreciated.

, I'm assuming I cannot tie an entire new bathroom into an existing drain run? OK!

First off, You assume correctly. Just as long as you have slope and vents you're good to go. However, this is a major project that you're planing and a permit must be pulled and the job inspected.

Do you have the necessary tools and skills, plus a knowledge of State and local plumbing codes to pull it off? If you're hesitant about tearing into your plumbing, let me suggest hiring a plumber to lay it out and do the job while you act as a helpe,r and do the scutt work to hold down labor costs.

I can't lay the job out for you without being on the job. It sounds like you're going to have a difficult task just cutting into the main, let alone installing the bathroom group. I'll put up a diagram of how we do our bathrooms in my area. The lavatory vent will wet vent the group, but be aware that your code might not allow wet vents.

Click on back and tell me your level of experience and knowledge of plumbing, and we'll go from there. You know that if we can help, we will.

Regards, Tom

First, thank you for a quick repsonse!

I've designed and built one house, but that was back in 1997 in a different state. The IBC is used here & I have some familiarity... and can find a copy online. Being a mechanical engineer, I think I can wade through the code to understand what's allowed in the venting design... maybe with a question or two answered online. Just never have worked with cast iron drain pipe... used only plastic in the past. I don't have a "chain cutter" for working with the cast iron. I've done plenty of copper work over the years, so the supplies will be straightforward.

The other option I have, alternative to tying into the cast iron stack, is to tie into the PVC portion of the drain that's buried & runs out into the back yard. Because of the location of the proposed bath, it would actually be a shorter run to tie into this buried PVC line vs running it back to the cast iron stack. What do you think of this as an alternative?

Working with cast iron can be OK if you use the right tools.

Here, you don't want to use a chain cutter... could very well crush or even cause a longitudinal crack in the entire length of cast iron you're working on and that would certainly make things even tougher for you.

Better here would be to pick up a Lennox Diamond sawzall blade and use a reciprocating saw to make your cuts. I would install a cast iron no-hub fitting into the cast iron stack... only real trick is to measure the fitting and then add 1/2" to 3/4" to that measure before marking the new measure on the pipe and making your two cuts.

Most important here is to SUPPORT THE WEIGHT of the cast iron piping above the cuts (and below if the pipe doesn't go right into concrete... see images). Here you can use a RISER CLAMP(s) and some 2"x4" studs to the floor... see image.


To finish, you would install new No hub clamps onto the cast iron fitting ends, flip the rubbers back on themselves and insert the fitting into the stack... SS clamps get slid onto the cast iron pipe before inserting the fitting... flip the rubber sleeves down into place, slide the clamps over the sleeves and tighten everything up real well.

Once the cast iron fitting is installed you will transition to PVC off the branch of the cast iron fitting using a SHIELDED TRANSITION CLAMP (see clamp picture below) made for cast iron (one side) and PVC on the other side.

In my last pic.below I show a PVC fitting with pipe in it... I really suggest using a nohub cast iron fitting here!

Good luck and let us know if you need more info. OK?. :)

Mark

Thanks guys... this is clear and makes sense.