Hey, well no your spa should not be loosing 1" of water in 24 hours. The only things that should remove such water is:

1. If the water is just leveling off over the waterfall/spill over.

2. There is some backflow into the pool through your plumbing. I know most spas usually have a flow device to prevent backflow but sometimes depending on how you have your valves it can flow back through the plumbing.

If neither of those are suspected then I'd say you have a leak. I'm still a pool newbie but thats my take on it.

Eric