The way some spas were manufactured (e.g., completely foam-filled), or the way they were installed can make it at times, impossible to find a leak. If you are absolutely sure that the leak is not coming from the equipment area (i.e., pump seal, loose connection, etc.), then before you have your deck pulled up, the foam dug out, or possibly even concrete removed, we suggest an alternative solution that works most of the time.
The product "Fix-A-Leak" was developed and patented in 1979. It was designed to seal holes 3/16" and smaller. Once the leak is sealed, it becomes permanent. We have used this product in the past and have been very impressed with it's performance.