a) The lowest pressure that a vacuum pump could ever hope to
attain is 0 bar
The height of a column of fluid (assuming the vapour pressure in
the tank is 1 bar) then maximally is
Delta(p) = rho g Delta(h)
Delta(h) = Delta(p) / (rho g)
= 10^5 N/m^2/(733 kg/m^3 * 9.81 m/s^2) = 13.9 meter = 45.6
ft
b) If Delta(p) is not 1 bar but ( 1 - 0.194) bar = 0.806 bar, then
the depth needed is reduced by a factor 0.806
So then
D = 0.806 * 45.6 feet = 36.75 feet
Although gas station owners lock their tanks at night, a gas station owner in your neighborhood...