In this video we will be discussing how to calculate TDH or Total Dynamic Head. TDH is the total amount of system pressure, measured in feet, where water can flow through a system before gravity takes over. Put simply, you need the TDH in order to correctly size out your pump.

To Calculate TDH we need to know 2 variables:

1) The vertical rise measures the vertical pipe in feet
2) The friction losses: The loss of flow in a system due to friction created by factors like: pipe type, size, fittings, horizontal runs of pipe, etc.

1. To calculate the vertical rise, you need to determine how many feet your water will have to travel upwards before gravity takes over. Simple take the lowest point the water sits and subtract it from the highest point
2. To determine the friction losses: First, acquire your flow rate in GPM. Once you know that, you can add the vertical and horizontal piping lengths of your system to the equivalent length of fittings in feet. Each type of fitting has an equivalent value measured in feet; refer to your preferred manufacturer’s friction loss chart for these values. Now, take the sum of the total length of pipe (including fittings) and divide it by 100.00. (As per 100 ft. of pipe)

Next, you need to determine your friction loss multiplier by using the following information:
• Type of piping
• Schedule of piping
• Diameter of piping
• Required flow rate

Once you have this, use a reference “Friction Loss Chart” from your favorite manufacturer to determine the friction loss multiplier.

Finally, plug all your variables into the following formula and you’ll have your answer;

[Total Length of Pipe (With Fittings)/100] X Friction Loss Multiplier = Total Dynamic Head

In summation: To size and buy the correct pump for whatever application, you need to know your required GPM and your required TDH. By following the steps above, you should have no problem choosing the pump that’s right for you.