K is called the loss coefficient of valve or fittings. K factors for commonly used valves are given in Table below

Valve or Fitting		K Factor
Globe valve	Wide open	10
	1/2 open	12.5
Gate valve	Wide open	0.20
	3/4 open	0.90
	1/2 open	4.5
	1/4 open	24
Return bend		2.2
Standard tee		1.8
Standard elbow		0.90
45° elbow		0.42
90° elbow		0.75
Ball check valve		4
Union socket		0.04