Total dynamic head (TDH) is the total resistance a pond pump must overcome to move water from the pond to the waterfall. It includes the vertical height water must travel (static head) and resistance from pipes and fittings (friction loss).
You can use the following simplified method to estimate TDH when selecting a pond pump.
How to estimate total dynamic head
- Measure the vertical height. Measure from the pond's water surface to the point where water enters the waterfall or filter. This is the static head.
- Account for pipe length. Add approximately 1 ft (0.30 m) of head for every 10 ft (3.05 m) of pipe between the pump and waterfall.
- Account for fittings. Add approximately 1 ft (0.30 m) of head for each additional fitting, such as an elbow or valve.
- Add the values together. The total provides a rough estimate of your system's total dynamic head.
Example calculation
For a waterfall with:
- Vertical height: 4 ft (1.22 m)
- Pipe length: 20 ft (6.10 m)
- Additional fittings: 2
The estimated total dynamic head is:
4 ft + 2 ft + 2 ft = 8 ft (2.44 m) of head.
This is a simplified estimate, not an exact measurement. Actual friction loss depends on water flow rate, pipe diameter, pipe length, pipe material, fittings, and other restrictions. Smaller pipes and higher flow rates can significantly increase friction loss.
How to use your estimate
Use the estimated total dynamic head with the pump performance charts in the Aquascape pump selection guide to determine how much water a pump can deliver at that head.
Remember that a pump's maximum flow rate decreases as head increases. Choose a pump that delivers your desired flow rate at the estimated operating head, not simply one with a high maximum flow rating.
For installations with long pipe runs, undersized plumbing, numerous fittings, or other restrictions, a more detailed friction-loss calculation may be necessary.