Cast Iron pipes-How long do they last & what can destroy them????

radiohead999November 6, 2006

Hello everyone.

A cast iron sewage pipe under my property needs replacement because there is a break in the line. I was wondering how long do these iron pipes last? The building is about 30 years old and so are the pipes.

In terms of normal wear and tear, what can damage iron pipes? Things that run through that line is anything of regular usages from the toilet, and the kitchen. Will things from the toilet eventually ruin the pipes? How bout washing dishes from the kitchen? The grease? oil?

And I know it may be hard to say, but how much would the work cost? I was told its about 10 feet underground, and digging will be needed.

Any help will be appreciated, thank you!

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ThatÂs a good first posting, RH. I think you are a smart inquirer.

Not that it matters.

But, hereÂs a reply. Your query, "How long do these iron pipes last," is a great new question. The answer is, it depends. Aw Shucks.

You see, if there are no extenuating circumstances, cast iron pipes are about as good as it gets. Of course, that is for old installations, such as yours. You can hardly beat PVC for new work.

That said, if you have CI and it is properly installed, it will outlive you. I had a bad experience in a rental house. The idiots (sorry, they arenÂt that clever) installed CI piping when the sewers came thru after septic systems were the norm.

It would have been just fine, except that the DIYers were not up to the task. They installed the new lines with a reverse slope. That is, instead of having a natural drainage slope of ¼" per foot, they installed the new pipes so that there was a small negative slope; but altogether it was a total fall.

That is, the 4-inch pipes were fully adequate to take the flow, but the negative slope meant that there was a dip in the run that always was wetted with sewage. This failed, as luck would have it, years later when I became the owner. The CI pipe (No-Hub) which is a different recipe than the older version, was eaten-thru, so that is eventually formed a leak.

The lower surfaces were rotted away and the leaks were evident as thin skin on the bottom-most outside diameter. This could easily occur, unseen, underground. CI pipe is a premium product. If you have it, it should last a "lifetime." Whatever that means. But I canÂt help thinking PVC is a superior product. I have also used ABS. It, too, is a great material for the purpose. It is much lighter in weight, but very durable.

I would like to see it become the standard.


    Bookmark   November 6, 2006 at 11:54PM
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One of the larger hospitals in the area was initially constructed in the mid-1960's. Cast iron drain pipes. The place where the cast iron has deteriorated fastest in that installation is the kitchen area. They concluded that the acid in the discarded orange juice was the culprit. Chemical drain cleaners cannot be good for the cast iron. The "once a month" chemical treatment suggested by some is good for the bottom line of the chemical maker, but not for the pipes.

    Bookmark   November 7, 2006 at 6:59AM
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The repeated use of acid to clear drains eats cast iron pretty badly.
'Organic digester' is sulphuric acid, and eats CI very nicely.
I have seen a cuple of commercial installations over the years that used acid on a frequent basis to keep the drains from kitchens running.
One of them had eaten out the entire bottom of a 6 inch cast iron drain, and was only found when the waste backed up under the slab and cam e up from cracks in the floor.
The landlord sued the tenant for destroying the lines and won.
In typical use the oron corrodes slightly to expose the graphite inthe metal matrix, and then most of the corrosion then proceeds very slowly.
In a correctly designed system CI should last at least 30 years, and many installations are pushing 80-100 years with no problems in residential use.

    Bookmark   November 8, 2006 at 9:24AM
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