Hot Water Recirc Pump Head
Pump head from pipe length, fittings, target flow.
Example
You enter
- Pipe length one-way (ft) 100
- Fittings count 8
- Target flow (gpm) 4
- Internal diameter (in) 0.75
- Material copper
You get
- Pump head 6.79 ft
- Pressure 2.94 psi
- Equivalent length 16 ft
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
Formula or tableRecirc head = friction loss along the recirc loop at design flow + minor-loss allowance for fittings. Sized for the longest closed-loop circuit per ASHRAE Handbook hot-water recirculation guidance.
Source and editionASHRAE Handbook (HVAC Applications) by name; Hazen-Williams (AWWA M11 5th ed.) for friction.
Free accessASHRAE Handbook licensed; ASHRAE 90.1 read-only at ashrae.org.
What governsEstimate. AHJ and licensed plumber / gas fitter govern. Verify against the IPC / IFGC edition adopted in your jurisdiction.
API field namespipe_length_ft, fittings_count, target_flow_gpm, internal_diameter_in, material, head_ft, pressure_psi, equivalent_length_ft
- Design recirc flow entered by the user (no default); size it from the loop's heat lossASHRAE Handbook
- Fitting allowance each fitting adds an equivalent length, default 2 ft, to the straight pipe before Hazen-Williams is appliedengineering practice