The Easiest Way to Apply the Concept of Equivalent Length of Fittings in the Plumbing Design: Plumber

In a plumbing system design, an aspect that cannot be lost sight of when determining the pressure required for the proper functioning of the installed fixtures, is the effect that the number of fittings or accessories like elbows, tees, reducers, and valves, among others, have on the system head loss.

That is why it is so connected to the concept of the Equivalent Length of fittings, so as to include, in the calculation of friction losses in pipes, localized losses generated by the fittings installed in it.

In simple terms, the theory of the Equivalent Length of Fittings provides that for each fitting there will be an equivalent length of “dummy” pipe that generates a friction head loss equal to the localized head loss generated by this fitting, so that, when using a calculation equation for friction losses (which are generally dependent equations of the pipe length analyzed), a length calculation is made by the sum of the length of straight pipe and the equivalent lengths of those fittings installed in it.

Thus we find, either in the bibliography of fluid mechanics and hydraulics, manuals, and standards of plumbing design or manufacturers’ catalogs, Tables of Equivalent Length of Fittings, which are presented to each diameter and each fitting, the respective equivalent length.

How does Plumber include the concept of Equivalent Length of Fittings?

In Plumber has been implemented this Table of Equivalent Length of Fittings, in the Fittings Manager:

From this dialog, which is accessed from the Configuration tab → Fittings panel, the user may set the equivalent lengths according to the characteristics of the fittings used in the plumbing design.

It is important to note that the inclusion of the equivalent lengths specified in the Fittings Manager in the calculation of head losses will only take place when we set the option Equivalent Length in the Head Losses Calculation Panel of the Configuration tab:

Otherwise, i.e., when the option “Developed Length Increment” is selected, the concept of equivalent length of fittings will be applied increasing the length of each pipe section by the specified percentage.

What Fittings does Plumber include for Plumbing Design with the Equivalent Length of fittings concept?

From its initial version (1.0), are incorporated the 11 accessories presented in the figure.

Additionally, if required, we have defined two “generic” fittings, referred in Fittings Manager as User Defined. In them, as with the other fittings, descriptive text can be changed to adapt it to user preferences.

How to add or remove a nominal diameter to the Table of Equivalent Lengths (in fittings manager)

To maintain consistency between the diameters of pipes used for the plumbing design with Plumber and the fittings to be included in each section, we have centralized the addition and removal of diameters in the dialog that appears when you press the button in the Configuration Tab → Diameters Calculation Panel:

The Diameters Manager Dialog allows you to add, delete, and modify pipe diameters used in the plumbing system design and, in turn, allows to specify the aspects highlighted below:

1Friction coefficient used in the Hazen-Williams formula. 2Nominal or Maximum Pressure the pipes are designed to handle. If, during the plumbing system design, the program detects that the calculated pressure at some point is greater than the value specified here, it will present a warning to the user to make necessary modifications, if applicable. 3Buttons to add or delete a row (a diameter) to the table. When you create a diameter in this table automatically, when loading Fittings Manager, a new column will be shown with the specified nominal diameter, thus it provides the necessary fields to establish the Equivalent Length of Fittings for this new diameter. Similarly, pressing the Delete Diameter button will remove simultaneously the respective diameter from the table in the Fittings Manager. 4This option defines the way in which the plumbing design will be made, namely as the diameter will be selected for each pipe section. To do this, Plumber will perform the diameter calculation (according to criteria selected by the user: by speed or by unit head loss) and, based on that value will select the next inside diameter (Superior) if the box is checked. If not, it will select the inside diameter above (below) to the calculated.

Plumber Fittings Table

As we begin to add pipes, with their respective accessories or fittings, the program will define the accessories table, accessible from the tab of the same name in the Plumber’s main window:

In this table we can review the fittings assigned to each section of pipe and its diameter and, of course, the corresponding Equivalent Length of Fittings calculation in the project.

It is important to warn that, if we choose to select the option of head losses calculation by Developed Length increment, it will not be presented the last two columns (the equivalent length) in this table, because it is no longer part of the calculation. Thus, the information presented is similar to a list of materials:

Knowing aspects related to the inclusion of the concept of Equivalent Length of Fittings in the plumbing system design with Plumber just helps to learn how easy it is to add accessories to the pipe sections of our water supply network, as will be explained in this other tutorial.