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244 Chapter 7 Water Distribution Systems: Modeling and Computer Applications

• For the pipes, you can edit the data as you have been by clicking each element individually, and
then entering the appropriate data. However, this method can be time consuming, especially as
the number of pipe elements increases. It is often easier to edit the data in a tabular format.
• Click the Flex Tables button in the toolbar at the top of the screen. Select Pipe
Table from the available tables.
• The fields highlighted in the Pipe Table are output fields. The fields in white are input
fields and can be edited as you would edit data in a spreadsheet.
Warning: The pipes may not be listed in the table in numerical order. You may want to sort
the pipe labels in ascending order. To do this, move the cursor to the top of the table and
place it on the Label column. Right-click, select Sort, and then select Sort Ascending.
The pipes should then be listed in numerical order.
• Enter the correct pipe lengths into the Length (User Defined) column found on the Pipe
Table. Also enter the pipe diameters and Hazen-Williams C value. Close the Pipe Table.
• Note: You can customize which columns appear in the Pipe Table by clicking the Edit
button in the toolbar at the top of the table. Table columns can then be added or re-
moved as desired.
Running the Model
• To run the model, first click the Compute button on the main toolbar. Arrows should
appear on your layout screen indicating the flow direction in each pipe. If you click on
any of the objects, you will see the results in the dialog. You could look at the results for
all similar objects by opening the Flex Tables button. For example, if you want to look at
flows in all the pipes, select the Pipe Table. To examine the flow through the system over
a 24-hour period, select the Calculation Options under the Analysis menu. Double-click
the Base Calculation Options, then in the Time Analysis Field select EPS. Set the start
time to 12:00:00 a.m. and the duration to 24 h. The Hydraulic Time Step of 1 hour will
provide sufficient output for the purpose of this tutorial. Click the Compute button.
• The software provides a couple of different ways to determine whether your model meets
the target demand: Scroll through the Calculation Summary and check to see if there are
any disconnected node warnings. When the level in tank T-1 drops to the minimum tank
elevation of 99 m (tank level of 9 m), the tank closes off, preventing any more water from
leaving. This closure will cause the linen factory to be disconnected from the rest of the
system (that is, it will not get the required 20 L/s).
OR
Close the Calculation Summary window and select the Linen Factory junction. To create
a graph of the pressure at this node, click the Graphs button in the main toolbar.
Create a Line-Series Graph from the New button in the Graphs dialog. Select the
Pressure box in the Graph Series Options window, then close the options window. You
should see the calculated pressure at the Linen Factory and notice that it never reached
zero (no water pressure).

Answer

As you will see for this problem, all the pressures at the linen factory hover around 465 kPa, and no
disconnected nodes are detected. Therefore, the pumping station can support the factory’s 20 L/s
demand for a 24-h period.

Solution to Part 2:
• Add another demand to the Linen Factory node. To do this, double-click the Linen Factory
junction and enter into the Demand Collection field a second fixed demand of 108 L/s in
the row below the 20 L/s demand after clicking the Ellipse button. Close the dialog editor.