To figure the water pressure from a mounted tank, measure the height of the
bottom of the tank (outflow) to the level of the spigot.   In inches that is
inches of water convertable to psi with the proper conversion factor.  Do
remember that an additional 40lbs up top can make handling differences when
employing evasive maneuvers to keep from being skewered by one of
BenTsyncros out of control dokas.