Been chasing a leak. Realized it after regular salt and CYA loss. I know it isn't leaking out of the discharge/backwash port or any of the above ground plumbing/filter/pump. It also seems to only be when pump is running as I pass the bucket test with the pump off. I assume it's underground somewhere but no evidence (wet spots etc). Also, I get air bubbles from ONE return jet - the one closest to the pump. Any ideas where to begin? Return side typically more prone to failure than the suction side? I'm about ready to contact a leak detection company.