Fluid logic in four steps
The fluid tools are one chain. Area from diameter, velocity from flow, regime from Reynolds number, pressure from head, power from flow and head.
Logic
Area is πd²/4. Flow 0.02 m³/s in a 150 mm bore is about 1.13 m/s. Darcy head loss then needs a friction factor you supply: f 0.02 over 50 m is about 0.43 m. The same idea on a 100 mm pipe, 40 m long, holds 314 litres. Use pipe flow and pipe volume.
Reynolds number is ρvD/μ. Water at that 1.13 m/s in a 150 mm pipe, viscosity 0.001 Pa·s, is about 169,500, usually turbulent. The 2,300 and 4,000 bands are a convention. Use Reynolds number.
Static pressure is ρgh. Ten metres of water is 98.1 kPa. That is gauge pressure under a still column, not a pump duty. Use pressure from head.
Hydraulic power is ρgQH. 0.02 m³/s through 15 m, water, is 2.94 kW. At 70% efficiency the shaft figure is 4.20 kW. Pipe loss is only in the head if you have already added it. Use pump power.
Last checked 2 October 2026. The logic is the textbook relationship named above. It is not a code check. See standards these tools do not replace.