A while back, I had to tackle the tough and messy job (along with the help of a professional plumber friend) of replacing our old cast iron waste stack. A leak had formed and, needless to say, the cast iron needed replaced immediately since we didn’t welcome the thought of sewage behind our wall and in our basement, and the leak would only continue to get worse.
I see cast iron waste stacks in older homes often while performing inspections. Cast iron used to be a popular choice for waste piping prior to plastic, and some people even still choose to have it installed. One main benefit to cast iron is that, unlike plastic, it is very quiet. You likely wouldn’t even know when water is flowing through it. In addition, cast iron waste stacks have great longevity. The one I replaced in my own home lasted 120 years before it needed replaced.
Unfortunately, though, cast iron also has some major downsides. The metal rots from the inside, so there is generally no way to tell when the piping is corroded until a hole has formed through the exterior and it is too late to make a repair. And if a hole has formed, it is likely that the rest of the pipe’s interior is also heavily corroded. In addition – as you might imagine – cast iron is quite expensive, so it is cost-prohibitive for many people.
If you are building a house with an ample budget and are considering cast iron for its benefits, rest assured that the piping will last well beyond when you would need it to. But if, like many people, you have an old cast iron stack in an older home, be sure to keep a close eye on it since problems can creep up unexpectedly. If you do find yourself in the unfortunate situation of having to replace your cast iron stack, I would definitely recommend leaving the job to a qualified plumber and opting for plastic piping (PVC or ABS) since it is much cheaper and will also last a long time.
All in all, plastic piping is really the preferred choice for most newer homes and repairs nowadays… and for good reason. If you have a cast iron waste stack that isn’t too old and is still functioning fine, there is no immediate need to replace it; but if problems start to arise (as they inevitably will at some point) be sure to get on it quickly and to have the job done professionally.
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