Replacing entire soil stack...or not?

[Mculik5]

My brother is renovating (completely gutting) the bathroom in the house he just bought. House was built in 1955 and has cast iron DWV plumbing.

Among other things, he is relocating the toilet 90 degrees from it's current position to fix a "knee room" problem between the toilet and the tub (it's a small bathroom). Doing this obviously requires moving the toilet waste pipe, which will require reconnecting to the soil stack.

He is concerned about making the new connection, which will be PVC to cast iron. Instead, he is thinking about replacing the entire soil stack with PVC. The house only has this bathroom and a random toilet in the basement, so the stack is simple, but it still seems like a pretty large undertaking.

What are your thoughts on this?

Thanks.

 

[Jadnashua]

CI is still considered the Cadillac drainage system, primarily because it is MUCH quieter when it drains, and in some situations, (mostly in high rises) because it doesn't burn.

There are reliable methods to connect PVC to CI. If the CI is in good shape, it may not be worth the effort to replace it. If it isn't, that's another story.

 

[Sponsor]

 

[Terry]

1955? I like the idea of replacing the stack above the first floor. Cast does rust through over time.
If the old cast is copper sized, like 3-1/8", 4-1/8" on the outside, I use a copper sized coupling for that. New cast is ID plus 3/8" and plastic is a little larger than that.
So if the OD is X+1/8", go copper by plastic on the mission style couplings.

As a plumber, this is what I use. The metal wrap makes them code legal.

This bathroom was a little tight too with the tub.

 

[Mculik5]

Thanks.

Are there other options besides Mission couplings to make the connection? Do professional plumbers use them, or is there a better but more complicated way?

Also, are the Mission couplings legal to use anywhere you can make a cut/new connection? I don't have a picture right now, but I believe there is an existing Y in the soil stack for the old toilet location. It would be very easy to cut this Y before the flange where it joins the next piece of cast iron and start the PVC run from there instead. Is that legal?

Lastly, any inspection pitfalls with these couplings?

Thanks again.

 

[Jadnashua]

You need either a banded coupling or, if you remove a pipe from a hub, you can use a properly sized rubber donut to transition between materials. Removing a pipe from a hub entails drilling out a bunch of lead, then prying what's left out. Then you can remove the pipe and clean out the oakum. You need to measure the ID of the hub and get the proper sized donut. Too big, makes it nearly impossible to insert the new plastic pipe...too loose, and it will leak...just like Goldilocks...it needs to be just right. They come in numerous incremental sizes.

 

[Mculik5]

I've attached a picture of the situation.

If he were to cut the cast iron where I've indicated in the picture, install a Mission coupling, and connect PVC components to move the toilet connection over to near where the heating duct is, would that be:

- Legal
- Something that most inspectors won't give you a hard time about
- High quality; not likely to leak or cause problems
- The right way to do it

Two other questions:

1. What size PVC is best to use?

2. To Terry's point about replacing the stack ABOVE the first floor, the house is only one floor with a basement. Are you recommending replacing everything above the basement?

Thanks.

 

[Bluebinky]

I'm not a pro and don't look at this stuff all day every day, but is that a lead or cast iron closet bend?

 

[Cacher_Chick]

More often than not, old cast iron on the horizontal will fail long before old cast iron on the vertical.

 

[Terry]

This looks to be a lead bend. On those I normally remove the lead bend, pick up a rubber sleeve made for going inside the cast iron hub and run plastic from there.

Or you might consider replacing some of what you have with new pipe. You could increase some of the pipe sizing and fix some of the bends and fittings.
If you do decide to cut and drop the cast, be aware that it is very heavy, and should be supported before any cuts are made.