> "So, basically we had a 15-foot head of pressure over the filter."
Or 6.5 psi. (15/2.31)
231 is such a useful number, I write it down three times for junior engineers:
And then I add the units:
231 cubic inches in a gallon
2.31 feet water head in a psi
231 mph - highest recorded wind speed at ground level, Mount Washington, 1934
Showing, once again, the superiority of traditional units.