New to the forum, bought a house with a 16x32 in-ground gunite pool last year. This is the first year of dealing with pool maintenance, chemistry, etc.. Everything has been rather smooth, except for when I turn my pump off, I am receiving pressurized blowback into the pool, the pressure is high enough to dislodge the skimmer basket. I have read multiple threads on this site regarding the issue, and consensus seems to be suction side air leak but I really don't believe that's it.
My issue seems a little unique when I remove the plastic cover from the pump, I hear a gurgling noise and water drains out. After I release the air from the system, when I turn the pump back on I don't have prime, and even once I regain prime the filter pressure is poor, so poor I cannot run my heater. When I am receiving the blowback, filter runs fine and everything else works.
My pool guy believes it is the sand filter. My sand filter is the old school (not even sure how old) stainless steel ball type. PSI is around 22-24 (pool guys says for my size should be 16-18) He recommends a new one, but before I incur that expense I wanted to come here for any ideas. I've given it a good backwashing, but that takes the pressure out of the system (psi stays the same) and the filter functions poorly again. It could be very dirty and sand gunked up, I have no idea the last time it got a deep clean. I've never taken apart a sand filter, and I don't even think I could get parts for the one I have, but I'll try it if its a possible solution (I can upload pictures if needed).
Basically when I get the blowback, the pump functions fine, pools gets clean, heater can stay on. When I get the pressure out, then I have issues and my filtration doesn't work properly.
Thoughts? I appreciate any help that can be provided