Honestly, do we have to spell it out?

1. All pipe is be the very best quality, preferably tubular or pipular, is to be hollow throughout the entire length and is to be made of long hole, surrounded by metal centered around the hole. Certification must be provided to the Engineer that in all cases, the O.D. of pipe will exceed the I.D. to avoid the hole being on the outside.
2. All pipe is to be supplied to the jobsite free of rust, as this can be more readily applied at the jobsite and is to be cleaned free of covering such as mud, tar, barnacles or any form of manure before installation to prevent lumps under the paint.
3. All pipe over 500 feet in length must have the words "Long Pipe" clearly painted on each end so that the Mechanical Contractor will know it is a long pipe. Pipe over 1000 feet in length must also have these words painted in the middle so that the Mechanical Contractor will not have to walk the full length of the pipe to determine if it is a long pipe or not.
4. All pipe over six inches in diameter is to have the words "Large Pipe" painted on it, so that the Mechanical Contractor will not use it for small pipe."

O.D. and I.D. being, of course, outer diameter and inner diameter.

This was taken from a scan of a document marked as follows:

It was found on pages 18 and 19 of the Mechnical Systems Specifications.