What is the total force on the bottom of a swimming pool?

The weight of the water above it. Obviously the deep end has more pressure on it than the shallow end. Water weighs 8.35 lbs per gallon . All things being as should the weight of the water is supported by the ground below it, the pool liner or shell is simply a barrier between the water and the dirt.

It's commonly said to be +1Bar/for every 10 meters.