Geeeeee only thing that could take 300 or more gallions is a UFO...
For someone to pump that much water out soooo fast,,they would have need a pump and I would have heard it.....
Nope it was a concrete slab...didnot look like a river near my spa when I looked.
And yes the spa was filled when I put the chemicals in.
about 2 hours later 3/4 of the water was gone,water was just a tad above the foot wells.....
No signs of a leak...........
Its been a week since the tech saw no leak,,,and the spa is still full....
And I was not smash at the time,,,,I would know if if put chemicals into a emtry spa.....................Thanks......JT