I have the 3600 also and the impeller shaft has broken twice (because
the impeller housing broke and caused a misalignment). Both times I got
a free replacement from pondliner.com

Remydog wrote:
I can't believe it, but after looking at the shaft material, I'm not
surprised. It appears to be a flimsy piece of plastic, so I suspect that the
torque of the motor, combined with any sort of load, results in breakage.

I'm hoping the place that sold it to me will replace it today without too
much hassle.

Anyone else having problems with this pump?

MSK