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Currently renovating 2 bathrooms that are above each other and the full plumbing stack is exposed. The house is from the 1950's and has a cast iron drain stack and connects to the bathtubs and sink drains/venting with galvanized pipe. All looks to be in decent shape overall, but does it make sense to change it now while things are open?

I ran the water on high and all seems to be flowing and draining as expected.

The basement is unfinished so I can easily make repairs to the main drain line (And 1st floor bathroom) that comes down from the drain stack if a horizontal line ever breaks or needs repair. Its the vertical in the wall that I'm most curious about, and the galvanized drain from the 2nd floor tub. A plumber friend told me they normally just leave the vertical stack since it typically never has issues but the horizontal drain lines in the basement are worth considering but they can easily be fixed later in the unfinished basement.

Is it common to replace the entire cast iron drain stack when you have walls open, or is that cast probably fine since its a vertical drop? How about the galvanized pipe from the tub drain that still looks like its visually in good condition?

Thanks!

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    Cast iron probably good for many more years. The galvanized not to sure about, would at least to take apart a small section to check the inside.
    – crip659
    Sep 6, 2022 at 14:44
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    I DK the entire answer, esp. regarding the galv. but one advantage of iron pipe is that it's pretty quiet, replace with with plastic ABS drain line and you might get more noise. Sep 6, 2022 at 15:13
  • "Should I" is going to get about as many saying "yes" as "no", because without being there to do an onsite inspection, there's no real way we can know. Cast iron can last centuries (witness: bridges & buildings in the UK), but yours might be just about ready to quit. There's no telling.
    – FreeMan
    Sep 6, 2022 at 16:04
  • Thanks everyone, lots of solid points and things to consider.
    – RocketManZ
    Sep 6, 2022 at 21:28

1 Answer 1

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If you are doing a gut reno of a bathroom you should replace any 70 year old galvanized pipe you find in the walls except maybe dry vents.

Replacing 70 year old cast iron with PVC is a coin toss. It won't last forever, but it might last another 50 years and your PVC pipe and rubber ferncos might not. We don't know. There aren't any 100 year old 3 inch PVC risers.

I was in the same position. I had the walls open, didn't obviously need to replace the vertical cast iron. It would add about $2000 to an already expensive project. Before I decided, my other vertical stack, in a bathroom I was not renovating, developed a crack and I had to rip open the kitchen and a bathroom to repair it. Since they two stacks were the same age and material I decided to do them both. But you, without a clear indication that your stack is reaching end of life, might have to roll the dice.

It's definitely the case that you can hear water running through PVC drains in the wall, but not through cast iron.

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  • Great points all around. I think I'll do some good visual inspecting, and possibly cut a few of the galvanized pipes at some points where I can then continue on with a Fernco and PVC, that way I get a really good look on the inside joint areas and see how they look. I may even have a small camera I can snake it just to get an idea of if the walls are slim. I'll also ask a plumber who I have doing some other work his opinion, but I didn't want to do that without getting some input first since my guess was the verticals may be ok.
    – RocketManZ
    Sep 6, 2022 at 21:28
  • A camera is a good idea. There are some good self-contained ones (don't need phone or laptop) with multiple cameras for front and side view for under $100. It's very hard though to see hairline cracks in cast iron. A pressure test might help, though out of my league and I don't know if that's wise in old cast iron.
    – jay613
    Sep 7, 2022 at 2:16

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