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I am planning to finish my basement on a house from the 1940s. One part of that is to level the floor. In preparation for that I am addressing high spots and past concrete patches.

One spot I notice has a metal piece sticking up. After carefully chipping away pieces I was able to determine it was a copper pipe with a flattened end.

There appears to be a perforation, and nothing is leaking (gas, water, etc.).

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Has anyone seen something like this before? If not, would it have been a practice to use copper pipe in concrete as some form of reinforcement?

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  • I guess that's one way to stop thieves stealing copper !
    – Criggie
    Dec 26, 2023 at 20:38

2 Answers 2

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Small-diameter copper tubing was used to pipe fuel oil, stored outside, to an oil burner. For protection, it was often embedded below a thin layer of concrete. You can see images and information at Inspectapedia and Hearth.com.

If the house had an oil burner and tank that have been removed correctly, there's no concern about that bit of tubing under concrete.

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When you're laying a concrete floor, it's very easy to lay pipework first and concrete it in. When the pipes need upgrading or replacing though, it's not practical to remove them though, so new pipes are run in other places and the old ones are simply left in place. They should be capped off so that the pipe doesn't become a route for damp to get into the house, but that's all.

In the 1940s, copper was just starting to replace older cast iron pipes. Lead pipes were the norm for low-pressure internal water, but mains water came in on cast iron pipes. Anything you really didn't want to leak - gas or oil, for example - also ran in cast iron. My 1929 bungalow has an old cast iron pipe in a concrete pad under the old pantry.

Cast iron is brilliantly resilient, and pipes weren't too expensive. The big problem for cast iron though is joining pipes, because the only way is for the plumber to form threads on the ends of each pipe and join them with appropriate-sizes nuts. The threads had to be cut by hand; an old-school plumber once told me that it took a couple of hours per end of pipe, so labour costs were much higher. Cast iron pipes can't be bent either, so every bend needed the pipes to be cut and joined with a corner. Copper can easily be bent though, and joining copper only needs soldering which is quick and easy. Once copper piping became cost-effective for plumbing, it was a no-brainer to use that instead.

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  • That's interesting, about cutting the threads! I wonder if they used taps and dies (just like I do whenever I need threads) or something else. Dec 26, 2023 at 17:52
  • @TannerSwett Yep, tap and die by hand, apparently.
    – Graham
    Dec 26, 2023 at 19:27
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    I couldn't imagine it taking more than a few minutes to thread one end of a pipe, even with hand tools. Electric pipe threaders sold today take under a minute. The "old-school plumber once told me that it took a couple of hours per end of pipe" hopefully meant it took hours to thread an entire house full of pipe, and not a single piece of pipe?
    – Xen2050
    Dec 27, 2023 at 2:41
  • @Xen2050, the modern threading machines will generally be used on steel tubing. Graham is discussing that in the context of cast iron pipes. I imagine that would be more difficult.
    – Transistor
    Dec 28, 2023 at 0:05
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    @Xen2050 there are several difficulties with cutting a thread into cast iron. Firstly, it's cast rather than extruded, so it's not perfectly circular. Secondly, high stress will cause it to shatter or chip rather than deform, so cutting with a tap or die takes repeated passes with different size dies. (This is also why it can't be bent.) Thirdly the metal has irregular crystalisation, so the torque does not remain constant. All of this means that it's not simply a matter of setting the die and then spinning it around for some count; rather you have to check torque & alignment continuously. Dec 28, 2023 at 10:06

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