A pump that looks correctly sized on paper using static head and pipe friction alone can still come up short in the field — because every elbow, valve, reducer, and pipe entrance along the route quietly steals a little more energy from the water. At the advanced level, a complete TDH calculation accounts for every one of those losses, across pipelines that change diameter and material mid-route. This guide walks through the full four-term TDH equation with two completely worked, realistic pump applications.
The Complete TDH Equation
At the system-optimization tier you worked with three terms. The full, advanced-level equation adds a fourth:
TDH=Hs+hf+hv+hL - Hs — Static head (elevation difference, source to discharge)
- hf — Friction head loss along straight pipe runs (Hazen-Williams)
- hv — Velocity head at the point of discharge
- hL —