Fluid head loss through fitting and valves can be calculated from:

h fluid = 'K' x v ² / 2g


'K' = manufacturer’s published 'K' factor for the fitting

v = velocity of fluid

g = acceleration due to gravity


In many systems where pipe lengths are relatively long, the effect of the fitting losses may be considered to be minor losses, and could be ignored during initial assessment.


If a partially open valve is part of the design, the effect of the valve should always be considered as the valve loss may be large.


Pipe Flow Expert has a database of valve and fittings ‘K’ factors and calculation wizards for:


  • gradual enlargements
  • gradual contractions
  • sudden enlargements
  • sudden contractions
  • rounded entrances
  • long pipe bends


For further information on this subject please refer to ‘Flow of Fluids through valves, fittings and pipe’ - Crane Technical Paper No. 410