Yesterday I changed water in my spa.Prior to draining I opened the breaker at my 50 amp gfci.I verified the display went blank.After filling the spa I closed the breaker at gfci and had no display on spa so I went to breaker panel in the house and found the 50 amp breaker had tripped.In addition I opened the breaker on gfci to see if it would still trip and it did so I believe I can rule out spa. Any thoughts.By the way everything is less than 6 months old and I've changed water once prior with no incident.

In addition I opened the breaker on gfci to see if it would still trip and it did so I believe I can rule out spa. If you turned on the breaker in the main panel, and can also turn on AND trip the GFI breaker, the problem is almost definitely in the spa itself.

The gfci does not trip.Only the breaker in house breaker box after approx 30 secs.I opened the gfci breaker to isolate the wiring from tub and still tripped house breaker.

Oh, re-reading it I see. You say you left the GFI breaker open and the one in the main still trips.

Wow, that is weird. There IS then obviously an issue with the circuit somewhere. I don't like the sound of waiting 30 seconds to trip. That implies that it is not a direct short, which could mean burning wires as a worst case scenario.

Ok thanks.What bothers me is everything including wiring is new #6 thhn,50 amp breaker in house/garage and square d 50 amp gfci.Could either of the breakers do that or possibly moisture?Worked perfectly until yesterday when I killed power.How could I isolate gfci box?Or maybe I should get an electrcian to do some load testing.

This definitely sounds like something an electrician should check.

OK thanks for your time