Sorry this is going to be a long one guys. I just can't figure this out, I desperately need your ideas. Last year I wired up a pump for a waterfall in a pond. Just a little residential one, in a customers backyard. It ran fine for about 7 months. It is about 100 feet from the house panel. I buried I believe 3/4 or 1 inch pvc. One hot, one neutral, one ground. I up'd the thhn to number 10 guage. Went from a breaker in the panel to a gfci which fed another plug right next to it in a four square weather box with a weather proof cover. The kind that you can keep plugged in all the time. He runs this pump 24 7. Well the gfci tripped in February. He called us this spring about a month ago. I went out there and couldn't get it to work. Took off the gfci and put just a reg. duplex on it and it tripped the breaker in the house. Ran a cord from the house and it again tripped the breaker in the panel. I finally figured out it was the pump. Manufacturer said ya we had a bad batch. So we installed a new pump from a different manufacturer. Plugged it into the circuit and ran it with no Gfci. It ran for two days straight. Cool I went back out there put the new gfci from before back in and all was well. Well a week later it trips the Gfci again. I go out today with digital apm probe in hand. With everything on including low volt lights it only draws 9 amps amps. I have 20 amps ran out there and 123 volts reading on my digital tester. So I put a brand new 20 amp GFCI in and after about 2 minutes it trips. No spike in amps on the tester. So I go to home depot and get a GFCI 20 breaker. Install it and make the 2 plugs regular duplexes no Gfci outside now just inside in the panel, turn it on clean up pack up still running everythings great. Nope tonight I get a call and its tripping the GFCI breaker now. I am totally lost on what else to do. The only thing I haven't done is replace the thhn 10 in the pipe. I don't think I need too though because just the GFCI was tripping and not the breaker. I believe a pump for a pool can not be on a GFCI as long as it is a single plug at a lock in type plug. Is it true for pumps for ponds. I getting the code book out right now. just thought I would see what you guys think might be happening. What are the chances of 2 pumps from 2 different manufacturers being bad. Please help