How to Use the Pump TDH Calculator
Selecting a pump requires knowing total dynamic head (TDH), not just flow rate, so you can match it against a pump's head-flow performance curve. This calculator adds up suction static head, discharge static head, pipe friction head loss, minor (fitting) losses, and any required residual head at the discharge point to give TDH.
Static head is the actual elevation the liquid must be lifted through — if the source is below the pump, that's suction lift; if the discharge point sits above the pump, that's discharge head. On top of that, friction inside the pipe and losses from valves, elbows, and other fittings both add resistance the pump must overcome.
Finally, if the discharge side needs a minimum pressure to operate — a sprinkler head or nozzle, for instance — that pressure gets converted to feet of head and added in. With TDH calculated this way, you compare it against a pump manufacturer's head-flow curve at your required flow rate to select the right model.
Actual pipe friction loss is normally calculated precisely from pipe length, diameter, velocity, and roughness using the Hazen-Williams or Darcy-Weisbach equation — this calculator takes an already-computed friction loss figure as an input rather than deriving it. Have a mechanical or fluid systems engineer confirm the final pump selection.
Frequently Asked Questions
A pump has to overcome not just the elevation change (static head) but also pipe friction losses, fitting losses, and any residual pressure needed at the discharge point. Total dynamic head is the sum of all of these, and it's what you plot against a pump's head-flow performance curve to pick a model.
Friction loss is typically calculated from pipe length, diameter, flow velocity, and roughness using the Hazen-Williams or Darcy-Weisbach equation, or looked up from a manufacturer's head-loss chart. This calculator takes that already-calculated friction loss value as an input.