I just scrolled down and didn't get a chance to read all the posts so this may be in there already. I have had the luxury of troubleshooting a hot tub with one of their techs before. A major cause of the gfis tripping is that the heater pack of the hot tub goes bad. If you can get a hold of the manufacturer,have them talk you through disconnecting this and see if it still trips. It's nice to be able to prove to the tub owner that it's not the electricians fault.
