Total dynamic head with Hazen-Williams friction and K-value minor losses, plus NPSH available. For water.
All calculations run in US customary units internally and are converted for display. Water properties are taken at the entered temperature.
V (ft/s) = 0.4085 × Q (gpm) / d², d = pipe inside diameter (in).hf (ft) = 0.002083 × L × (100/C)1.852 × Q1.852 / d4.8655. L includes any added equivalent length. Valid for water at ordinary temperatures, turbulent flow.hm = ΣK × V²/2g, g = 32.174 ft/s². Each line uses its own velocity. K values are pre-filled for each fitting; open Advanced to view or edit them. Foot valves: hinged-disc + strainer K ≈ 2; poppet + strainer typically K 6–8 (7 used). Include an exit (K = 1.0) on the discharge to account for the velocity head leaving the pipe.h = P (psi) × 2.3067 / SG.TDH × SG / 2.3067.hatm − static suction lift − hf,suction − hm,suction − hvap, referenced to the pump centerline for an open (atmospheric) source.P = 14.696 × (1 − 2.25577×10⁻⁵ × zm)5.2559 psia.log₁₀ PmmHg = 8.07131 − 1730.63 / (233.426 + T°C).Warnings flag line velocity outside ~2–10 ft/s (0.6–3 m/s), suction velocity over ~6 ft/s (1.8 m/s), suction lift over 25 ft (7.6 m), NPSHa at or below zero, and NPSH margin under 10% / 3 ft (0.9 m) of NPSHr (or NPSHa under 10 ft (3 m) if no NPSHr is entered). Blank or zero C, inside diameter or flow stops the calculation with an error rather than showing misleading results. These are rules of thumb; always confirm against the selected pump's curve.
Results are estimates for planning and training. Verify critical designs against manufacturer data and applicable codes.