Tutorial #3: Calculating A Standpipe System with A Pump Only

The system you will be calculating is shown below.

It is a standpipe system with a pump only and no city supply. The method used here can be applied to pumps supplying water to sprinkler systems as well.

To satisfy NFPA Standards, you must set the two most remote hose valves on the most remote standpipe to 250 GPM @ 100 PSI minimum and then add 250 GPM for each additional standpipe as you approach the water source up to a maximum of 1250 GPM.

Start a new HydraCALC file, save it and name it. Here is what the HydraCALC screen should look like:

Note that T31 is entered for fittings at each hose valve. This is for a tee and 31 equivalent feet for the valve. Enter the values as shown above.

Select Water Sources from the View pull-down menu.

From the Edit Water Supplies dialog box, select Supply 1 and then press the Edit Pump button.

The Edit / Create Pump Curve dialog box will appear.

Enter a Rated Pressure of 140 PSI, a Rated Flow of 1000 GPM and a Churn Percentage of 120%. Next, press the Make NFPA Curve button. This will calculate pump curve coordinates and place them in the cells of the Output Curve. You can save this pump for future jobs by selecting Save Graph from the File pull-down menu.

Press OK to exit.

You will return to the Edit Water Supplies dialog box.

The Pump Inlet, Pump Outlet and Connection must all be labeled PUMP because there is no city supply. Press the OK button to close the Edit Water Supplies dialog box.

Press the Calculate button. The Pre-Calc Questions dialog box will appear.

Set up the box as shown here. Hose valve H1 will be the Remote Point and PUMP will be the Source Point. Press OK to start the calculation.

The Hydraulic Calculation dialog box will appear when the calculation is complete. When you press the View button, a detailed report will appear. You will find that hose valve H1 is most remote with a flow of 250 GPM at a pressure of 100 PSI. H2 and H3 will have higher pressures.