By Brooklyn Water Commissioners' formula: Head-0 000467 49 X 100+ 25 X (2 + 0 397)2 -1 '07 feet. In this case, the pipes being very much corroded, the resistance is greater, and more head is necessary. By Lane's formula: Head -0'000625 X 100+0'25X v2= 1 foot. (Pipes in average condition). A correspondent has asked us what is the difference of friction in a pipe, under 15 pounds pressure and under 150. We will use Lane's form ula in making the necessary computa tions for the answer, though the same method would answer with either of the others.