I have an ICON 10 spa (about 4 years old) that keeps tripping the GFI breaker about 20 seconds after I turn in on. I replaced the GFI plug but it still happens. The weird thing is that if I put the jets on high (the pump has 2 speeds) it doesn't trip the breaker. It's a 110V unit.

I saw some posts about disconnecting things from the main panel inside the unit. The only thing I disconnected that kept it from tripping was the blower/pump. The heater is behind the panel I think and I didn't see any easy way to disconnect it.

How can I tell if it's the heater or the pump or something else?

(I'm guessing it's the heater because I think I remember someone telling me once that 110V spas can't run the heater and the pump on high at the same time, which would explain why it doesn't trip the breaker on high, because the heater isn't on!)

You're exactly right about the heater. The element can be disconnected either at the heater terminals or where the wires from the heater connect to your control.

Thanks spishex. Can you (or anyone) answer a real newbie question: is there a way to replace the heater element without removing the entire heater assembly? From the pictures I see online it looks like the element is inside of the assembly and connected to power through the two little holes on the top so I'm thinking that there isn't.

If the element is replaceable (some small heaters are welded together) then you'll have to at least remove a section of plumbing from one side or the other that you can slide the old element out of and the new one in through. The easiest situation would be if you had a small section between the pump and heater with unions on each end and 90 between. Take that off and you would have all the room you need. This is assuming that you have enough clearance inside the control box to remove the two 3/4" nuts holding the element in place.