Friction Loss

Friction loss in piping refers to the amount of pressure that is lost as water moves through the piping. As the pipe diameter decreases or flow increases, the amount of friction loss or pressure drop increases as well. There are two ways to conserve pressure in piping systems. The first way is to decrease the flow rate of the system. If this is not a viable option, you can also increase the diameter of the pipe as a means of conserving pressure.

Below are charts for friction loss (pressure loss) for different types and diameters of pipe at various flow rates. The left side of the column shows various flow rate expressed in gallons per minute. Along the top of the chart are the different pipe sizes. Underneath each pipe size is the velocity of the fluid in motion expressed in feet per second (ft/sec) and pressure loss per 100′ of pipe.

The shaded area of the chart shows where the velocity exceeds 5 feet per second. Avoid using pipe sizes and flow rates that fall within this area as this exceeds the maximum safe flow for piping systems.

If you already know the flow rate of your system, the type of pipe used, and the length, then you can enter that information into the Piping Friction Loss Calculator to automatically calculate the pressure loss.

Friction Loss Charts

Class 160 PVC (SDR-26)

Class 200 PVC (SDR-21)

Schedule 40 PVC

Schedule 80 PVC

Type K Copper

Pipe Friction Loss Calculator

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