T&F 6 min solutions problem #4

I calculated this problem using Cameron Hydraulic data.

I found the Hydraulic Diameter (Table 16.1 in MERM) for a 2"x2"square cross section to be equal to L.

So, Hydraulic Diameter=2".

I calculated the flow to be 22.44 GPM.

Looking in Cameron for water at 2" SCH 40 Steel (I know its asphalt, but figured this was close enough), I found 1.076 ft/100ft.

so, at 40ft, this is a head loss of 0.43ft.

with 1ft head=0.433psi, 0.43 ft x 0.433psi/ft=0.186 psi

The correct answer shows 0.19 psi using Bernoullis.

Is this method also correct, or did I just get very lucky?

I dont have the problem in front of me but my guess is.....good. I think your answer and the method to obtain your answer is also correct.