Use head metres,flow litres/hour on each line.
Read a pump curve with a worked example →
How it works
Total head = the vertical water-level difference + your separately entered friction-head estimate. Between two manufacturer points, the tool uses straight-line interpolation. In a synthetic curve of 2,400 L/hour at 1 m and 1,600 L/hour at 2 m, 1.5 m gives 2,000 L/hour. This is a mathematical example, not a product rating.
Where the estimate stops
Do not assume maximum flow and maximum head describe a straight curve. Copy at least two relevant documented points, in increasing head order. The tool rejects extrapolation. Pipe diameter, length, fittings, valves and branches affect friction; enter a defensible estimate separately or use zero to examine lift alone.
Verify the installed result
Measure actual return flow after installation where possible. A fit to a published curve cannot account for every plumbing detail or dirty pipe. Keep drain capacity, noise and manufacturer operating limits separate from the flow calculation.
Source: EcoTech Marine’s explanation of head pressure and plumbing factors. Use your model’s curve; no brand preset is supplied.
Plan saltwater batches · Estimate ownership cost · Keep your tank records