Pressure drop due to pipe fittings can be estimated by the equation, P$/=4$f$,($Le$/$D$)($V$2/2$gc$)$ where, Le $=$ equivalent length of straight pipeline which will incur the same frictional loss as the fitting and D $=$ diameter of the fitting. The value of $($Le$/$D$)($dimensionless$)$ for $45$ elbow and $180$ close return bends would be respectively around

$5$ and $10$

$45$ and $75$

$180$ and $300$

$300$ and $500$