This has been going on since the time the company who built the pool 10 years ago (my first season owning it) had opened the pool (month ago).
When the pump starts the water sprays out of the rear flange (where the motor is attached). They tightened it but still.
It does not leak, it is only during the start (very pronounced) and stop (not as pronounced but noticeable).
I think it is not normal. I am also not sure what would happen if the water did not have any place to go - obviously the burst of pressure is large, wouldn't it blow the pump or pipes? Or is it as simple as changing the gasket and it should hold?