Reviewed by: David Chen, P.E. (Professional Engineer) | Updated: October 2023
Optimize your pumping system’s efficiency with our professional Total Dynamic Head Calculator. Accurately determine the total resistance a pump must overcome by calculating static lift, friction losses, and pressure requirements.
Total Dynamic Head Calculator
Total Dynamic Head Calculator Formula
$$TDH = h_s + h_f + h_p + h_v$$
Where: $h_s$ = Static Head, $h_f$ = Friction Head, $h_p$ = Pressure Head, $h_v$ = Velocity Head.
Formula Reference: The Engineering ToolBox – TDH Principles
Variables:
- TDH: The total equivalent height that a fluid is to be pumped, taking into account all losses.
- Static Head ($h_s$): The vertical distance the pump must lift the water.
- Friction Head ($h_f$): The equivalent head loss due to pipe walls and fittings.
- Pressure Head ($h_p$): The head required to maintain specific pressure at the discharge point.
- Velocity Head ($h_v$): The energy of the fluid due to its velocity ($v^2/2g$).
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What is Total Dynamic Head?
Total Dynamic Head (TDH) is the total equivalent height that a fluid is to be pumped, taking into account all friction losses in the pipe and the elevation change. It is the most critical factor when selecting a centrifugal pump or sizing a motor.
Without an accurate TDH calculation, a pump may be undersized (failing to deliver required flow) or oversized (wasting energy and potentially damaging components through cavitation or vibration).
How to Calculate Total Dynamic Head (Example)
- Measure Static Head: If you pump water from a well 20ft deep to a tank 30ft high, your static head is 50ft.
- Determine Friction: Use charts to find head loss for your pipe size. Let’s assume 10ft of loss.
- Calculate Pressure: If the tank requires 10 PSI, convert to head (10 PSI × 2.31 = 23.1ft).
- Sum it up: $50 + 10 + 23.1 = 83.1$ ft TDH.
Frequently Asked Questions (FAQ)
Does pipe diameter affect TDH? Yes, smaller pipes significantly increase friction loss ($h_f$), which raises the TDH.
Why is velocity head often ignored? In many low-speed systems, velocity head is less than 1ft and is neglected for simplicity, though it’s technically part of the equation.
What happens if TDH is calculated incorrectly? If TDH is underestimated, the pump will operate at a lower flow rate than designed. If overestimated, the pump might run off its curve.
How do I convert PSI to Head? Multiply PSI by 2.31 (for water) to get the equivalent head in feet.