How to Calculate Total Dynamic Head For a Pump

How to Calculate Total Dynamic Head For a Pump


Today we’ll be discussing how to
calculate TDH. Before we dive in, what is TDH and why is it so important?
TDH stands for total dynamic head which is the total amount of system pressure,
measured in feet, where water is flowing through a system before gravity takes over Put simply: you need the TDH in order to
size out your pump. To calculate TDH we need to know two variables: First, the vertical rise which measures
the vertical piping in feet Second: the friction losses which is the
loss of flow in a system due to friction created by factors like horizontal runs
of pipe, pipe type size, fittings, etc. To calculate the
vertical rise you need to determine how many feet your
water will have to travel upward before gravity takes over. Simply take the lowest point the water
sits and subtract it from the highest point. To determine the friction losses first
acquire your flow rate in GPM. Once you know that you can add the vertical and
horizontal piping length 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 manufacturers’
friction loss charts for these values. Now take the sum of the total length of
pipe including fittings and divide it by 100 as per 100 feet 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 and 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
* friction loss multiplier equals your total dynamic head. In summation to size and buy the correct pump for your
application you need to know your required GPM and your required TDH. By following these steps you should have
no problem choosing the pump that’s right for you.

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