I have a 20,000 in ground gunite pool. There are three returns (two to spa and one to main pool) and three coming back to the pump (main drain, skimmer and cleaner) I have an Aquarite salt generator and heat pump. Pool is 4 1/2 years old. Pump is a Hayward Super II 2HP with a Hayward cartridge filter.
Everything was fine until a couple weeks ago when I noticed the pressure dropped from 20 lbs to 10 pounds and the filter basket did not fill compeltely and there is about 2 inches between the water level and the basket lid.. It does not mater which if I use the main drain, skimmer or cleaner, the pressure does not move off of 10 PSI and the filter basket is not filling completely with water and there seems to be about 2 inches of air in the filter at the pump. I have replaced the o-ring and that did not solve the pressure problem.