This is a really fiendish problem, but we may have outsmarted it.
Ordinarily, the dimensions of the pool wouldn't matter, because the pressure only
depends on the depth of the water ... you always find the same pressure at the
same depth below the surface, whether you're in a pond, a lake, a bathtub, an
ocean, or a swimming pool. So our first instinct was to calculate the pressure at
6-ft down, since your pool is 6-ft deep.
But wait! Why is the quantity of water given ? Could it be that the pool is not
completely full and sloshing over the rim ?
Volume of the full pool = (12 x 30 x 6) = 2,160 cubic feet = 16,157.9 gallons.
Ah hah! The pool is not full!
Those 11,500 gallons fill it to only (11,500/16,157.9) x (6-ft) = 4.2704 feet. (rounded)
The pressure under 4.2704-ft of water is 1.841 psi(rounded)
(Using 5 psi = 11.6 ft of water, which we found somewhere on the www.)
One cubic foot of water is 7.4805 gallons.
There are 7.48052 US gallons per cubic foot.
1 cubic foot of water is 7.48052 US gallons.
141.06 gallons
One cubic foot = 7.48 US gallons.
One cubic foot of water is 7.4805 gallons.
There are 7.48052 US gallons per cubic foot.
There are 7.481 gallons in one cubic foot.
1 cubic foot of water is 7.48052 US gallons.
This cylinder will hold up to 3,760.11 gallons of water.
One cubic foot of water is about 7.48 (7.48052) US gallons.
141.06 gallons
One cubic foot = 7.48 US gallons.
A cubic foot of water contains just under 7.5 gallons of water.
One cubic foot of sea water contains about 7.5 gallons.
13,594 US gallons of water.
One cubic foot contains about 7.48052 US gallons or 6.229 Imperial gallons.