Solution
From the energy equation. the required pump head rise F-A is equal to the pressure drop due to friction from A-F through the system. But to find this, only the circuit with the greatest pressure drop is chosen. This is ABCC/DEF, the longest circuit. Circuits ABEF and ACDF are ignored. (It is possible in unusual cases that one of these two shorter paths may have a greater pressure drop if it has items with great resistance. Such cases must be checked.)