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Thread: Soil Waste Pipe

  1. #1

    Default Soil Waste Pipe

    Is there a way to readily tell the difference between a clay pipe and a cast iron pipe?

  2. #2
    DIY Senior Member Nate R's Avatar
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    I thought it would be obviously by looking at them?


  3. #3
    Moderator & Master Plumber hj's Avatar
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    Default pipe

    Since there is almost no similarity between the two, other than they are both round and carry drainage, all you have to do is look at them. Clay is red and cast iron is black or rusty brown. Clay breaks if you hit it with a hammer, cast iron breaks if you hit it with a hammer many times in the same place. Clay pipe is seldom smaller than 5 3/4" o.d., cast iron comes in many smaller sizes and is usually at least an inch smaller in o.d. than an equivalent clay pipe. If you cannot tell the difference, then you probably should not be working on it.

  4. #4

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    I am almost sure that the pipe is cast iron because of the diameter. The reason I asked was because all the other stacks in the house are definitely cast iron, but the cleanout is red (like clay) yet sounds metallic if you tap it. I had a master plumber over this past weekend and even he said he could not tell just by looking at it....he would have to take it apart. I was assuming (shame on me) that if the other stacks were cast iron, then the underground soil drain would be the same. I didn't think that there would be cast iron stacks and a clay underground sewage line. And then when the master plumber said he could not tell without taking it apart, I was really confused. I agree....there is a vast difference between the two. But when a master plumber cannot readily tell, I thought I'd ask you people. So I asked the question. Is my plumber an idiot?

  5. #5
    DIY Senior Member Nate R's Avatar
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    Quote Originally Posted by WBB View Post
    I didn't think that there would be cast iron stacks and a clay underground sewage line.
    I thought that actually was a fairly common way to do it at one time?

  6. #6

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    Thanks, Nate. Now at least I know that it's a possibility.

  7. #7
    I&C Engineer (mostly WWTP) Lakee911's Avatar
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    Quote Originally Posted by Nate R View Post
    I thought that actually was a fairly common way to do it at one time?
    Actually, that's what I have at my house. Cast iron waste stack inside and clay outside. I had it cameraed twice and both times they said that its cast iron underground. I even saw it and it looked a blackish-brown-red color. However, when it was dug up, we found that it was clay!

    I pulled up a piece of the pipe--I saved it at home actually. The pipe looked like it was originally orangish-yellow color, but the inside and outsides turned black. You can see in a cross section of the wall, the color variations. This is consistent with what I read online. The clay tends to discolor as its exposed to contaminants in the soil and in the waste water.

    Jason

  8. #8

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    Jason - that is exactly the way mine looks. So I guess I will have to cut a piece out to see for sure and take it down to my plumbing store and ask them. As I said before, a master plumber glanced at it and said he could not tell without disassembling it. Thanks for the help.

  9. #9
    I&C Engineer (mostly WWTP) Lakee911's Avatar
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    Oh, you'll be able to tell once you get it exposed. If not, a couple strokes with a hacksaw and you'll know if its castiron or clay. FWIW, cast iron underground is rare (at least in these parts).

    Jason

  10. #10
    Plumber krow's Avatar
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    Cast iron underground was mostly used in commercial application (ei: restraunts) , especially for their commercial dishwasher drainage. Its not used as often anymore for underground. Only if specific specs call for high heat resistant piping.

  11. #11
    DIY Senior Member Nate R's Avatar
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    Yeah, when mine was camera'd I was told that most of my drain line is 6" clay. I have CI stack in the house, though.

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