Re: Hot water testing of the parallel and stock IC.
Cavitation bubbles are always on the output side of the pump. The bubbles are the result of boiling at low water pressure. As you go up a mountain the temperature to boil water drops, go high enough and water would boil at very low temperature. The bubbles of cavitation are cold steam and gases in the water. When these bubbles implode on the surface of the impeller say, they do severe harm due to the forces released.
To solve cavitation impellers need to be larger and rotate slower and be designed accurately. That's what I have read anyway.