I have to describe a technical system with several pipes. If I want to describe the location of leak, do I say:

The leak is located in/on/at pipe number one?

Which preposition is correct?

There is this ELL question: "on", "at", "in" as preposition of location

Maybe "in line number one" ("in line" is given there) is similar to "in pipe number one", but I am not completely sure.

Is there any native speaker who can help?

  • There are different combinations of prepositions that sound natural to me, however it would be simpler to say "Pipe number one is leaking."
    – sas08
    Commented Mar 4, 2016 at 22:22
  • "In/at" don't sound strange to my ears, though "at" would be a little more colloquial it wouldn't raise eyebrows. You could also say "coming from" if you wanted to be very clear that there wasn't another pipe inside pipe one leaking into it. I have to say I've never thought about it, but you're not wrong for tripping up on this. It's kind of weird when you think about it. As far as in implies direction and location it logically makes as much sense to say "out pipe 1" really, but that sounds super back-woods, Southern.
    – sas08
    Commented Mar 5, 2016 at 0:21

3 Answers 3


The leak is in pipe number one, at machine number three, on the second floor.

In implies that the something you're referring to (in this case, the leak) is integral to or part of the structure of the pipe. Since leaks are usually caused by the pipe wall (which is a structural, integral part) having a hole in it, you use in.

At implies somewhere around or in the vicinity of. That's why I used a machine as an example: if each machine is fed by several pipes, and pipe number one is one of those, then pipe number one is in the vicinity of machine number three, and you can say it's at machine 3.

On implies a spatial relationship: you can have on the side, on the top, or on the bottom. Without any specification, it's often taken to mean on the top or on top of. Assuming that machine number three isn't flying, it's probably sitting on the floor. If that floor is the second floor, you can say that machine number three is on the second floor.

  • I think at Pipe #1 could be acceptable, if the pipe was short enough. Also, on can imply much more than a spatial relationship (think on the mark, on the money, on time, on fire, on the phone, or on a roll). I can certainly say, "I have a cut on my finger," or, "I have a wart on my foot," and those don't necessarily mean "on top of" (more like "on the surface of"). Similarly, "a leak on the pipe" could work.
    – J.R.
    Commented Mar 4, 2016 at 19:29

It's nearly always a leak in the pipe...

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...but native speakers wouldn't necessarily object to at - particularly in contexts where "the pipe" is one of several discrete sections within a delivery system that can be conceptualized as single points chained together (which perspective would also permit on, though this is somewhat less likely).

But the notion of "correct" doesn't really apply here, since referents like pipes, wires, lines don't actually have specific "pinpoint locations". So you can talk about a break in the earth wire or a short-circuit on the live wire when you mean "somewhere along the length of the wire", but it's more likely to be a blockage at the waste pipe if what you mean is the blockage becomes apparent where the waste pipe starts (even though the blockage may actually be much further along - possibly somewhere beyond the other end of the waste pipe). And native speakers won't always be sure of the "best" choice of preposition.

  • I would not say nearly always, though often you would use in. But there are circumstances where you would much rather use at or maybe on. Commented Mar 4, 2016 at 18:31
  • I like the use of data and see your point for normal cases, however I would assume that most people are discussing pipe leaks in simple systems, and are not engineers.
    – sas08
    Commented Mar 4, 2016 at 22:08

The fact that you are referring to multiple, numbered pipes makes this an interesting question, with little precedent to build off of.

As FumbleFingers said, the usual preposition for leaky pipes is in, but we don't usually talk about numbered pipes in the context of diagnostic systems, so you have a bit more wiggle room.

The leak is located in Pipe #1.

You can't go wrong with that one.

The leak is located on Pipe #1.

In my mind, that could work. One meaning of on is on the surface of (which is why we hang pictures on the wall, or have lacerations on our arm).

The leak is located at Pipe #1.

It's not a conventional way to say it, but given a diagnostic system with several possible locations for a leak, I think at could be used – particularly if the leak could appear in several different location types and you wanted to use the same preposition in each message:

  • The leak is located at Pipe #23.
  • The leak is located at Connector D6.
  • The leak is located at Valve V-16

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