Pressures exerted from within the pool that also includes the internal weight of the vessel itself.

Buoyancy is the tendency of an object to come to rest at the level where its internal pressure (including the boat itself) balances its external pressure. Wood floats because the internal pressure of the water is higher than that of the wood. Lead sinks for the same reason.

This tendency is seen for every state of mass and energy. In classical mechanics this is called thermodynamics. In conclusion to identical vessels with identical volume of water, one fiberglass and one concrete ..... how many more pounds of internal pressure does the gunite pool have?

TO DETERMINE WEIGHT OF CONCRETE SLAB PER SQUARE FOOT

T = Thickness of slab in inches

L.L. = "Live Load" (Placing of concrete, men & equipment)

Use 40 lbs. per square foot (lb./ft.2)

Wt. FM = Weight of forms

Use 10 lbs. per square foot (lbs./ft.2)

L.L. & Wt. FM. = Use 50 lbs. per square foot (lb./ft.2)

Wt. Concrete = Weight of Concrete

Use 150 lbs. per cubic foot (lb./ft.2)

T/12 x Wt. Concrete + Wt. FM. = Weight per square foot of concrete slab

EXAMPLE 9" SLAB WEIGHTS:

9/12 x 150 lbs. = 112.5 lbs. per square foot (lb./ft.2)

Plus 50 lbs. L.L. & Wt. FM. = Total Weight of 9" slab

112.5 + 50 = 162.5 lbs. per square foot' for 9" slab

= 162.5 lbs./ft.2

A small pool could easily have a surface area, including walls of 1000 sq ft. or 162,500 pounds which equals 81.25 ton.

Now add in the water at 8.345404 pounds per gallon times your total gallons for total weight.

IMPT- Never, ever, for any reason drain your pool without consulting a professional. Always drain in stages to allow ground water to balance within the vessel.