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Plumbing is a single part of the industry that uses PIPE as a means of moving gas or a liquid.
Some of these other indus­ tries are refrigeration, industrial process piping, pneumatics, and hydronic heating.
Rigid pipe derives its’ name from the material it is manufacturing from and the size of its’ inside diameter.
Ex. 1/2 inch copper pipe, 75 mm cast iron soil pipe, 2 inch ABS plastic pipe.
Coiled or flexible pipe derives its’ name from the material and the outside diameter.
This can cause some confusion if someone is working on both pipes.
Ex. 5/8 inch coiled soft copper tube and 1/2 inch rigid copper pipe have the same outside diameter and use the same size of fittings.
Pipe in Canada is measuring in both Metric and Imperial units.

(millimeters and inches) This double measurement is because Canada using the metric system and the United States using the imperial system.
Many of the materials manufacturing in Canada and shipping to the U.S., therefore both systems continue to exist.

What is the thread engagement:

Thread Engagement is the distance the pipe fits into the fitting.


What is the fitting allowance:

Fitting Allowance is the distance from the center of the fitting to the end of the pipe.
This space must be there to allow the liquid or gas to flow through the piping system and to allow for the tube to pass through holes in a floor, wall, or ceil­ing.


Examine the types of pipe measurements illustrated below.

The most commonly used measurement is center to center (C-C), followed by center to end (C-E).
The cutaway view of the pipe joint shows that pipe does not reach the center of the fitting because the pipe must not block the openings of the fitting.
This forces us to make some calculations when cutting the pipe to a measuring length.
The space between the end of the tube and the center of the fitting is the “fitting allowance.”
The amount of space taken up by a fitting varies with the size and type of it.
The general rule is that the fitting allowance is close to the diameter of the pipe.
Ex. the fitting allowance for a 13mm pipe fitting is 13mm.

25mm = 1 inch
Roughly 6 mm = 1/,i inch

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