I have a 30x15 AGP with a Proline pump with regular filter and chlorine dispenser. The whole system is about 2.5 years old. Just this year (in the past month) have had a problem of an air pocket forming in the system and it hangs at the basket cleanout on the pump itself. Daily I have to shut the system down, loosen the cap and bleed the air from it. If I don't do it daily it works itself to the filter housing and I have to open the top vent and it will blow air out for a few seconds before I get water. I have no water leaks visible anywhere in the system and the water level is high enough that it's not sucking air down into the pump. I would think if it was a bad gasket that air was sneaking in you would see water coming out when the unit is shut down etc..
Anyone have any suggestions or ideas of where this air is appearing from all of a sudden?