Swimming pools blog

Hello
I have bubbles coming into one of my return lines of an inground pool
I recently aquired.
When I try to vacuum the pool, it the pump loses it’s pumping ability
until I re-prime it. The water level is about 2/3 way up the trap
door and does not looses any water.
I’ve learned that this is usually an air leak on the suction side.
What is the best way to check for leaks on a suction side? Can this
aloe be a worn pump impeller of something going wrong with the pump?
Thanks