System
Enter all three elevations from a common datum (for example site datum or geodetic). Total static head = discharge − low water level; it can be negative (downhill or siphon).
Pipe segments in series
Each segment can have several identical lines in parallel; flow per line = total flow ÷ number of lines. Fitting losses use the velocity in the fitting's own size.
Throttle valve (optional)
Pump curve (optional)
Enter 3 to 5 points from one pump's curve at the speed it will run. The curve is fitted with a least-squares quadratic and is not extended past your last point (shown dashed).
Results
How it's calculated
- System head H(Q) = net static + Σ segments [Hazen-Williams friction at Q/n per line + Σ K × V²/2g for fittings at the velocity in each fitting] + throttle valve + one exit velocity head at the final discharge.
- Hazen-Williams: hf (ft) = 0.002083 × L × (100/C)1.852 × Q1.852 / d4.8655, Q in USgpm per line, d in inches. C defaults to 135 for each new segment (presets 120 or custom); it is never carried over from a previous job.
- HDPE uses the true average inside diameter from the DR, OD × (1 − 2.12/DR), never the nominal size. Steel and PVC use schedule inside diameters.
- Fitting K values are typical published values for turbulent flow; actual fittings vary. The gate valve throttle uses the classic published K ratios for open, ¼, ½ and ¾ closed; the position from the reverse calculation is approximate, and gate valves throttle poorly beyond about ¾ closed.
- Velocity warnings are per line: below about 2 ft/s (0.6 m/s) solids may settle; above about 10 ft/s (3 m/s) friction, wear and surge rise.
- Valid for water and water-like wastewater in turbulent flow. Not for viscous fluids or thick sludge. See the disclaimer.
Related: pipe friction calculator · HDPE pipe dimensions · unit converter
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