How many gallons of water does it take to fill a 15 foot by 42 inches pool?

You need to figure the volume of the pool: width x length x height in feet, then multiply by 7.5 to get gallons. Assuming your ends are round, yours would be something like 15 x 27 (for the middle) plus 7.5^2 x pi for the circular ends, all times 4 feet for the depth, or a total of 2327 cubic feet. Multiply by 7.5 to get 17451 gallons.

Now, if you want an 8 hour turnover (recommended) then you'd want 2181 gal/hour, or 36 gpm. Add in a safety factor (partially clogged filter, etc.) and somewhere around 50 gpm should be fine. Don't overdo it, though, too much volume is not good either.

A: More simply put would be more like 12 t 18 hrs depending upon use or bather load - - how many people, dogs etc in pool for what length of time - 8 hrs would be the minimum if the pool were not used.