Heater circulation pump was stalling, reconditioned it, refilled tub, ran big pump several minutes to purge air. Turned on heat and about 15 seconds later GFI tripped. Now GFI trips as soon as heat is turned on. Everything works fine with heater unplugged,

well almost, there is a slow leak where the heater line returns to the tub, some kind of green gook holding the spud into the PVC elbow. How to fix the leak????

Suspect there was a bubble and wondering what kind of heater element fits into the heater (110v).