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.

Pinoke

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.

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.

I realize this is an ancient thread, but I was researching cast iron pipes because our home just had a pretty catastrophic failure with them. My house was built in 1966 - so its 50 years old now. The pipes are so corroded on the inside that they are closing up tight in places and have holes in others. Saw it for myself when they sent the camera in. I was at the point of having to snake my main line and clean out pipes 2-3 times a week just to flush the toilet. Im now in the process of having the foundation of my home jackhammered up to remove ALL the corroded failed pipes from one end to the other. I will have to replace tiling in all the bathrooms, and the kitchen, and the laminate flooring elsewhere, plus parts of the walls will need to come out. It will be over $30,000 to fix this. My neighbor had this done about a year ago and it cost him over $50K when all was said and done (he has one more bathroom and he had more expensive flooring). I tell anyone looking to buy a house. If it has a concrete slab foundation and cast iron underneath - DONT buy the house.

I owned a 1950s house with galvanized steel piping in the slab. In the 80s, when it started to get really corroded, I simply ran a new copper supply line from the meter to the house, and then ran copper piping through the attic and walls. I abandoned the old piping in place. There was no need for destructive demolition, and no need to remove the old piping . There were a couple of places where I had to make small openings in the sheetrock, but that was about it.

Kudzu - I have water supply in copper pipes in my attic already. My problem are the drain pipes. From Laundry, sinks, showers, bathtubs and toilets. Im pretty sure I cant get my toilet to flush up into the attic :)

Are you sure you had cast iron Marc? I have removed both cast and galvanized steel drain from my house and the galvanized showed what you explained, corrosion on the inside there was not much diameter left, the cast was fine for the most part on the inside. There was damage to the cast near a floor drain, I would suspect from cracks in the slab and possible exposure to chemicals on the exterior of the cast.

Ideally these days, one would use PVC underground and cast iron in the living areas for plumbing noise. If noise is not as large concern then PVC is obviously cheaper.

Marc-

How sure are you that you have a problem with cast iron drains? Have they been inspected with a camera? If they are not functioning well, it could be due to a number of reasons aside from corrosion. There are many ancient cast iron drains that still function. When I replaced my 40 year-old galvanized supply lines with copper, all the drains were just fine and I didn't mess with them. In fact, when I sold that house, it was almost 55 years old and the drains were still fine.

My house was built in 1940 with cast iron drain pipes under the basement, and in the last couple of years we reconfigured a basement bath and added a new drain (using PVC). Jackhammering the slab was not an easy job, but when we cut into the iron pipes I found that they were clean, and had very little corrosion. They were HD cast iron pipes, which I believe is typical for under-slab drains. It is a heavier cast iron than the pipes used for my main soil stack.

The galvanized drain pipes in the wall are another story. They have corrosion and build-up in the bottom of the pipes, and I've had one bathroom drain snaked twice to clear out the pipes embedded in the concrete under the tile. I wish I would have replaced all of them when I did my kitchen renovation.

Bruce