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In civil engineering, the words invert and obvert are used in the context of pipe elevations. I gather that invert means: interior bottom elevation of pipe, and obvert means: interior top elevation of pipe.

This is a diagram of a pipe with arrows labeling the various parts. The crown is the outer top, the obvert is the inner top, and the invert is the inner-bottom. It also illustrates the external and internal diameters, with Size = Nominal internal Diameter(DD) near the upper right corner, with an arrow pointing to the inner diameter

However, using the word invert in this context seems strange to me. To me, none of these definitions fit:

Invert (Merriam-Webster)

  1. a: to reverse in position, order, or relationship
    b: to subject to inversion
  2. a: to turn inside out or upside down
    b: to turn inward
  3. a: to find the mathematical reciprocal of
    b: to divide using fractions, invert the divisor and multiply

What does the dictionary version of invert have anything to do with pipes? What has been inverted?

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It has occurred to me that people might not like the fact that I've cross posted on two S.E. sites.. This comment might shed some light on the issue. Of course, a nitpicky point to make might be: 'Are the two posts different enough?' In my opinion, it's not worth getting upset about. – Wilson 13 hours ago
    
Ultimately, it's jargon. – Hot Licks 12 hours ago
1  
Nothing wrong with jargon: we even have a tag for it. By all means edit it in if that tag is appropriate here. I'm not sure it is (but then I trained as an engineer, so whether it's jargon or not may be difficult to determine). – Andrew Leach♦ 12 hours ago
    
@AndrewLeach I just tried, but it didn't take effect. It appears to already be categorized as a tag synonym of terminology, which the question already had. – Tonepoet 11 hours ago
up vote 7 down vote

See the noun part of invert at Oxford dictionary

An arch constructed in an upside-down position to provide lateral support, e.g. in a tunnel.

invert

So you see, the bottom concave part is like an upside down arch, which is in discussion here.

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up vote 7 down vote

The Century Dictionary and Cyclopedia s.v. Invert: In architecture, an inverted arch; specifically, the floor of the lock-chamber of a canal, which is usually in the form of an inverted arch, or the bottom of a sewer.

The bottom of the sewer is called the invert from a general resemblance in construction to an "inverted" arch. Mayhew, London Labour and London Poor, II 445.


A list of dictionary definitions from the Century Dictionary and Cyclopedia, with the quoted entry in a red box.

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