Don't know if your pool is a constant depth, or is sloped so please bear with me. Why not take a water meter reading (and make sure no water is being used in the house) and then measure the level in the pool - now add exactly 2" of water to the pool, then go read the water meter. (2" is an arbitrary number - you pick what you want to do.) This information will tell you how many gallons per inch to your pool. If the bottom is sloped you can use basic trig to figure its realative size. I think this method will be far more accurate than using titration results with reagents that are not of exact concentrations.

For instance I know that my pool is almost exactly 500 gallons to the inch.