How to Calculate Developed Length in Plumbing

The length of a pipe that is used in plumbing is an important calculation. This measurement helps plumbers to calculate the amount and cost of supplies needed for a project. Pipe length also is an important consideration when it comes to water pressure. The developed length of a pipe is a measurement that is conducted along the center of a pipe. This plumbing measurement also takes into account the lengths of the fittings on either end of the pipe.

Plumber connecting PVC pipes
credit: Comstock/Comstock/Getty Images
PVC is a common material used to construct pipes for plumbing.

Step 1

Align a tape measure along the center of a pipe and measure the pipe's length. Write down the measurement. For example, the pipe might be 8 inches long.

Step 2

Write down the appropriate measurement for the fitting that is used on the specific type of pipe. For example, the socket depth for a 1-inch plastic pipe is 3/4 inch.

Step 3

Multiply the fitting measurement times 2 to account for the fittings on either end. Using the previous example of a 3/4-inch fitting, you would multiply 3/4 times 2 to get 1 1/2 inches.

Step 4

Add your answer from Step Three to the length from Step One to get the determined length of the pipe. In this example, you would add 1 1/2 to 8 to get a determined length of 9 1/2 inches.