jlr26

HELP! Pump pressure starts at 18 psi but after 10 minutes it drops to 8 psi and the pump motor starts making load noises like it is straining. Water returning to pool becomes very low. I've noticed very few bubbles entering the return lines. Should I check the rubber seals on the cover lids over the strainers on the pump; rubber seal on the cartridge filter; or maybe I need to change a seal between the motor and the pump/impeller; or check the air relie valves for leaks? Any help would be appreciated.