Cast stack education


Old 02-18-14, 06:15 PM
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Cast stack education

I am starting to plan for a project that I would like to start during my summer holidays and need some help with planning work to a cast iron 4 inch stack.

Gutting it all top to bottom would be straightforward but most of the vertical is still in good shape and I am undecided what is the best approach.
The 2 elbows that join the toilets to the stack are the weak links.

Ironically they are the youngest parts in the system. The stack is 60 plus years and is barely marked, save for the 2 toilet elbows, which I am guessing are about 10-12 years old and look pretty beat up on the insides.

Both toilet flanges are lead peened over brass flanges.

Can I change the lower 1/3 or at worst, 2/3 of the stack for ABS and leave the heavier cast on the top 1/3?
Or is it an all or nothing type job?

The elbow on the upper level is joined with MG clamps now.
Can it be pulled and new cast line put in and sealed at the T on the main cast stack line?
Or is it MG always from this point forward?
I thought these joints were lead chalked, but can that be done on a vertical seam?
If I keep the cast, should I replace the lead sleeve and go to cast toilet flange or is it best to stick with the lead and brass flange?

A lot of questions, sorry, but i am really undecided how to tackle this.

Thank you,

The rotting inside view goes with the unpainted elbow on MG clamps.

Last edited by Kiton; 02-18-14 at 07:11 PM.
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Old 03-15-14, 09:43 AM
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If it were me I would not replace the entire stack unless it was really needed. If I was going to change out the entire stack I would do the entire stack. At 60 years old you should have some bells (on the cast iron) where the pipe slides into. They should be leaded. If that is true anywhere you need to change pipe you could simply unlead the joints (by heating up with a torch and getting the soft lead out with a screw driver. Be careful as cast iron will break. So if the branches (also called closet bends) to the water closets (toilets) need changed with new closet flanges you should be able to unlead the existing closet bends and replace with new ABS or PVC pipe (your choice) use an SV gasket (for the bell of the cast iron. Put something slippery in the gasket so the pipe will go in and make sure it is all the way in use a tape measure if you are not sure. If this does not describe your installation then post back.

Good luck
Old 03-15-14, 10:15 AM
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I would replace all in PVC 100% if I was to do it... I probably would not sleep well at night knowing I left 1/3 of it cast....
Old 03-16-14, 10:52 AM
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Thanks John and Mike,

I have about 3 and half months to plan this out before I start.
I have pretty well concluded I either change it all top to bottom or just the closet bends (thank you for the correct term John). Both of you agree it is all or nothing, the trying to save a section is a short cut I should not take. It will be 100 percent of it or just the bends.

All the current branches are lead chalked. In the basement there are 2 joints, (the bathroom sink and tub and the kitchen sink) that have had work done and are sealed with PC4. I have read that PC4 is not permitted in the USA but it is common up here. Those joints would be hard to modify from what I have read.

Having a welding background, I like the idea of lead chalking the joint, I can wrap my head around that easily. The donuts spook me a little, are they really trust worthy and will they last?
I have just broken down and accepted PEX over copper this year. :-o

I read a lead chalked cast iron closet flange will last 30 years. I can't find the life expediency of an ABS flange, claims I have seen on line vary a great deal.

Thanks guys, your advice is really appreciated.
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Last edited by Kiton; 03-16-14 at 11:08 AM.
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