How to Calculate Total Dynamic Head for Solar Pump Selection

Total Dynamic Head (TDH) is the total equivalent height that a pump must lift water, accounting for vertical lift, pipe friction losses, and pressure requirements. An accurate TDH calculation is essential for correct pump selection.

The TDH Formula

TDH = Static Head + Friction Head + Pressure Head

1. Static Head

This is the vertical distance the pump must lift water. It has two components: Static Suction Head (vertical distance from water surface to pump inlet) and Static Discharge Head (vertical distance from pump outlet to the highest discharge point). Add them together for total static head.

For submersible pumps, the static head is simply the vertical distance from the water level in the well to the discharge point at the surface.

2. Friction Head

Water flowing through pipes encounters resistance. Friction head depends on pipe diameter, length, material, flow rate, and number of fittings. Use this simplified formula:

Friction Head (m) = (10.67 x Flow Rate^1.852 x Pipe Length) / (C^1.852 x Pipe Diameter^4.87)

Where C = pipe material coefficient (140 for PVC, 130 for steel). For typical solar pump installations with PVC pipe, friction losses rarely exceed 5-15% of static head when properly sized.

3. Pressure Head

If water must be delivered at a specific pressure (e.g., for drip irrigation or pressurizing a tank), convert the required pressure: 1 bar = 10.2 meters of head.

Example Calculation

Well depth: 50m (static head)
PVC pipe length: 60m, diameter: 32mm, flow rate: 2 m³/h
No pressure requirement

TDH = 50m + 3.5m (friction) + 0 = 53.5m

Select a pump rated for at least 53.5m TDH at your desired flow rate. Always add a 10-15% safety margin.