you could always dye the water and attempt to "trace" the leak that way, otherwise like stated above make sure you remove panels, check pumps/equipment etc. when the pumps are running because often times a small leak in a fitting won't leak when the spa is idle but as soon as you turn on the pump(s) it will immediately leak. As far as the "fix a leak" stuff, I don't sell it, nor would I ever personally use it so someone else would have comment on its effectiveness over a large sample size, over the small sample size I have it has a 0% success rate