Junction Loss Equation

A pipe junction is the connection of a lateral pipe to a larger trunk pipe without the use of an access hole. The minor loss equation for a pipe junction is in the form of the momentum equation. In Equation 10-36, the subscripts “i”, “o”, and “1” indicate the inlet, outlet, and lateral, respectively.
EquationObject313374
Equation 10-36.
where:
  • h
    j
    = junction head loss (ft. or m)
  • Q = flow (cfs or m
    3
    /s)
  • v = velocity (fps or m/s)
  • A = cross-sectional area (sq. ft. or m
    2
    )
  • θ = angle in degrees of lateral with respect to centerline of outlet pipe
  • g = gravitational acceleration = 32.2 ft/s
    2
     or 9.81 m/s
    2
    .
The above equation applies only if v
o
 > v
i
 and assumes that Q
o
 = Q
i
 + Q
1
.