Leaking air into my pump

[FRUITCOVE]

Somewhere my system is getting an entrance of air causing the system to not operate properly.
What areas could be causing this to happen?
Inground salt, 16,000 gallon,Pentair intelliflow pump

[PoolDoc]

Suction side leaks can occur anywhere between the skimmer or drain, and the pump. Common locations include:
+ pump lid
+ threads where piping connects to pump on suction side (next to strainer)
+ unions
+ valve stems
+ stuck skimmer weirs ('gates' or 'flaps')