Water flow in steel pipes schedule 80 - pressure drop and velocity
diagrams in SI and Imperial units
The diagrams below indicates pressure drop for water flow through
ASME/ANSI B36.10/19 schedule 80 steel pipes.
The pressure drop calculations are made with the D'Arcy-Weisbach Equation.
Pressure Drop - SI units

- 1 Pa = 10-6 N/mm2 = 10-5 bar =
0.1020 kp/m2 = 1.02x10-4 m H2O =
9.869x10-6 atm = 1.45x10-4 psi (lbf/in2)
- 1 liter/s = 10-3 m3/s = 3.6 m3/h
= 0.03532 ft3/s = 2.1189 ft3/min (cfm) =
13.200 Imp.gal (UK)/min = 15.852 gal (US)/min = 792 Imp. gal (UK)/h
- 1 m/s = 3.6 km/h = 196.85 ft/min = 2.237 mph
Pressure Drop - Imperial Units

Friction Loss Table
Friction loss table in pdf-format.

- 1 gal (US)/min =6.30888x10-5 m3/s = 0.0227
m3/h = 0.06309 dm3(litre)/s = 2.228x10-3
ft3/s = 0.1337 ft3/min
- 1 ft/s = 0.3048 m/s
- 1 psi (lb/in2) = 6,894.8 Pa (N/m2) =
6.895x10-3 N/mm2 = 6.895x10-2 bar =
27.71 in H2O at 62oF (16.7oC) =
703.1 mm H2O at 62oF (16.7oC) =
2.0416 in mercury at 62oF (16.7oC) = 51.8 mm
mercury at 62oF (16.7oC) = 703.6 kg/m2
= 2.307 Ft. H2O
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