Pipe Sizing Criteria

Using PIPE-FLO® to Size a Pipe

by Engineered Software, Inc.

PIPE-FLO® sizing criteria can ensure the optimum pipe diameter is selected for a given flow rate thus eliminating the problem of undersized and over-sized piping.

Undersized pipes can lead to higher fluid velocities that can cause damages such as wall erosion, water hammer, surges, cavitation, and higher friction loss in the pipes.

Over-sized pipe diameters incur added costs including but not limited to the incremental cost of the larger pipe themselves, the control valves, flow meters and fittings associated with the larger housing, and the added infrastructure to support the weight of all the larger items.

Thus there is a balance between what is considered an undersized or over-sized pipe. The pipe sizing feature in PIPE-FLO can help with evaluate this balance.    

A pipe can be sized using one of three sizing criteria; Design Velocity, Head Loss per 100 (feet or meters) of pipe, and Pressure Drop per 100 (feet or meters) of pipe. The sizing criteria is specified in the Pipe Properties dialog box when creating a Pipe Specification.

Sizing Criteria

The Design Velocity Sizing Criteria is the desired average fluid velocity that corresponds to the design flow rate for the pipe. Resources like the Crane TP-410 can be used to determine a reasonable velocity for various applications.

Two other commonly used sizing criteria are Pressure Drop per 100 (feet or meters) and Head Loss per 100 (feet or meters).

Using the Pipe Sizing Feature

A Pipe Specification (with Sizing Criteria) and a Fluid Zone must be assigned to the pipe in order to use the Pipe Sizing feature.

Select the pipe to be sized, then click the Size field in the Pipe Design tab of the Property Grid window. With the Size field selected, click the  button to open the Size Calculator dialog box.

The Sizing Criteria and design value will be taken from the Pipe Specification. Enter in the design flow rate, then PIPE-FLO will select a size from the Pipe Specification that results in a velocity, dP per 100, or HL per 100 that is closest to the sizing criteria value.


Use the Pipe Sizing calculator to choose an optimum pipe size based on the sizing criteria. Additionally, consideration should be given to industry guidelines, local building codes, and pipe manufacture standards regarding pipe sizing criteria. Also future pipeline expansions are typically involved in the pipe selection process. PIPE-FLO®'s Pipe Sizing tool can be used to balance all these variables and help build confidence in the optional hydraulic system designs.