Applets are programs based on the java language that are designed to run on your computer using the Java Run Time environment. You will find an article on this topic as well as many other related articles on the web site of Light my pump at

This program is designed to help you predict efficiency values for centrifugal pumps for the purpose of preliminary power calculations. In the initial phase of a project, the pump's head and flow is calculated, a request for quotation is issued to pump manufacturers which then provide pricing and information on the pump that they recommend for the application. After the pump is selected, the efficiency can be obtained and the power calculated. So what happens if you need the power requirement prior to receiving the manufacturer's selection. Well you can do your own selection or you can use this applet and get preliminary power results quickly.

The efficiency is based on a chart (see the Pump Handbook published by McGraw Hill) that provides efficiency values for typical centrifugal pumps over a wide range of flow capacities. It is based on tests made with real pumps and represents the best average of the industry.

(This chart is reproduced from the Pump Handbook published by McGraw-Hill)

First input the values for rpm, flow, head and specific gravity (SG) into the textboxes on the right hand side and then click the calculate button. This will calculate the specific speed of the pump which is displayed at the upper right. The specific speed is calculated with this formula in North American units.

Then use your mouse to scroll over the graph. You will see changing values for specific speed and efficiency that correspond to the position of your mouse on the graph. When you are satisfied that you have the right specific speed for your flow rate CLICK on the mouse, this will FREEZE the efficiency display above the graph and the power will be calculated and displayed at the upper right. To THAW the efficiency display, click the image again and the efficiency values will be able to change with the mouse position. This is confirmed by the ON red caption. You can calculate the power at any time by clicking the Calculate button. The Calculate button also calculates specific speed. Make sure you have the correct specific gravity, the default value is 1.0, the same value as water at standard conditions. The power is calculated with this formula: