When the fluid is slowing through  the pipe, some energy (head) is lost to overcome hydraulic resistance. This loss of energy is classified as follows:

1.    Major loss:

The major loss of energy is due to friction. It is determine by Darcy-Weisbach formula or chezy resistance. This loss of energy is classified as follws:

h_f  = 4_f L V² / 2 g d   Darcy – Weisbach formula

h_f  = 4V² L / C² d      Chezy’s formula

Where f  = Darcy’s coefficient of friction

           C = Chezy’s constant.

The loss due to friction is much more in case of long pipelines as compared to other losses and hence it is classified as a major loss. It depends on roughness of pipe, length, velocity and diameter of pipe.

2.    Minor losses:

•    The losses due to disturbance in the flow pattern are called as minor losses.

•    It occurs due to sudden contraction or expansion, valves, fittings, bends etc and at entrance and exit form pipe.

•    In case of short pipe, minor losses are to be considered.

•    Whereas in long pipe, it does not makes any serious effect.

(a)    Loss due to sudden enlargement,

h_L = (V₁ – V₂)2/2g


(b)    Loss due to sudden contraction,

h_L = [ 1/C_c – 1]² V²/2g

h_L = 0.5 V²/2g It C_c is not given.


(c)    Loss at the entrance,

h_L = 0.5 V²/2g


(d)    Loss at exit from pipe,

h_L = V²/2g


(e)    Loss due to bends or pipe fitting,

h_L = KV²/2g

(f)    Head loss due to an obstacle in a pipe,

h_L  = [A/C_c (A-a) -1]² V²/2g


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