Water Pipe Sizing Calculation Example – Part 2: Determining the Effective Pipe Length

Refer the Part-1 of this piping system design calculations series to know the problem statement and the assumptions.

What is Equivalent Pipe Length Method?

This the way of converting the Tee bends, valves and other pipe fittings in terms of equivalent pipe length. This value is added to the already existing pipe length to calculate the effective pipe length. So that the permissible pressure drop in the pipe can be expressed in terms of pressure drop per unit pipe length.


Getting back to our pipe size calculation, we have 2 ball valves and 1 Tee bend apart from 7 meters of pipe line. And, also our initial assumption about the pipe diameter is 20 mm.

From the equivalent pipe length table it can be found out that

The equivalent length for the 20mm Tee bend = 1 meter

And, the equivalent length for the 20mm ball valve = 7 meter

So, the effective pipe length for our example= 1+7*2+7 meter = 22 meter


In the next part (Part-3) we will see how to calculate the permissible pressure loss using this effective pipe length value.

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