Essentials of Plumbing

MEASURING PIPES

The measurement for a length of pipe required for installation includes the amount of pipe engagement and the dimension of the fitting. This learning event describes engagement, fitting dimensions, and pipe length. The last section of this learning event explains how to use these three factors to determine the amount of pipe required for installation.

Engagement

Engagement for cast-iron soil pipe (single-hub). Different sizes of pipes require different amounts of engagement. A pipe engagement occurs when the spigot end of one pipe fits into the hub end of another pipe. A fitting engagement occurs when the end of a fitting fits into the hub end of a pipe. Always measure the distance inside the hub for a true pipe or fitting engagement.

Engagement for cast-iron soil pipe (single-hub).

Engagement for rigid plastic pipe (ABS and PVC). Different sizes of pipes require different amounts of engagement. Engagement occurs when the end of a pipe fits into the collar of a fitting. Always measure the distance inside the collar for a true fitting engagement.

Engagement for rigid plastic pipe (ABS and PVC).

Engagement for galvanized steel pipe. Different sizes of pipe require different amounts of engagement. Engagement occurs when the threaded end of a pipe fits into the collar of a fitting. Always measure the distance inside the collar for a true fitting engagement.

Engagement for galvanized steel pipe.

Engagement for rigid copper tubing (DWV). Different sizes of tubing require different amounts of engagement. Engagement occurs when the end of the tubing fits into the collar of a fitting. Always measure the distance inside the collar for a true fitting engagement.

Engagement for rigid copper tubing (DWV).

Fitting Dimension

The fitting dimension is also needed when determining the amount of pipe required for an installation. The fitting dimensions for all types of waste fittings are determined the same way. A fitting dimension is the distance from the center of the fitting to the end of the fitting.

Fitting Dimension

Measurement of Pipe Lengths

End-to-end measurement.

End-to-end measurement.

End-to-center measurement.

End-to-center measurement.

Center-to-center measurement.

Center-to-center measurement.

Determination of Amount of Pipe Required for Installation

Pipe-to-pipe. To figure the length of pipe required when using single-hub cast-iron pipe, use the following steps. The example given in italics is from the illustration below.

Measure the end-to-end distance from the place where the new pipe will be installed (42 inches).
Add the amount of engagement (42 + 6 = 48).
Take a double-hub pipe and cut off the one end. The remaining piece should equal the total (48 inches).

Pipe-to-Pipe Determination of Amount of Pipe Required for Installation

Example:
end-to-end engagement length of pipe required	+ =	42 inches 6 inches 48 inches

Pipe-to-fitting. The method for figuring the length of pipe required for a pipe-to-fitting connection is the same for all types of piping. Use the following steps. The example given in italics is from the illustration below.

Measure the end-to-center distance from the place where the new pipe will be installed (60 inches).
Subtract the fitting dimension (60 - 6 = 54).
Add the amount of engagement (54 + 2½ = 56½).
Cut a pipe the length of the total (56½ inches).

Pipe-to-Fitting Determination of Amount of Pipe Required for Installation

Example:
end-to-end fitting dimension engagement length of pipe required	- + =	60 inches 6 inches 2½ inches 56½ inches

Center-to-center. The method for figuring the length of pipe required for a connection between fittings is the same for all types of piping. Use the following steps. The example given in italics is from the illustration below.

Measure the center-to-center distance from the place where the new pipe will be installed (66 inches).
Subtract both fitting dimensions (66 - 5 - 5 = 56).
Add the amount of engagement for both fittings (56 + 2 + 2 = 60).
Cut a pipe the length of the total (60 inches).

Center-to-Center Determination of Amount of Pipe Required for Installation

Example:
center-to-center both fitting dimension engagement length of pipe required	- + =	66 inches 10 inches 4 inches 60 inches