When I turn on my pool pump it primes well psi at 30 and suction and return jets are strong. 30 minutes later the pump suction is lost and the pool circulation is lower or no circulation at all. The pool pressure still remains high at 30 psi. I notice that there is no water in the pool pump and I hear a bubbling sound in the top of sand filter. I have changed the sand, I have made sure that the air bleeder is in the correct spot and is not clogged, I have checked the O rings of the pump basket, the jandy valve and mpv and they were lubed as well. I have tried to blow out the line with the water hose and bladder. I have also used a shop vac, at both the skimmer side and pump side, I have checked the pump fan to make sure there are no sticks or twigs. When I turn the pump valve to the skimmer or main drain the pressure will drop to 25 psi for both sides. Is it possible to have an air leak?? I have sprayed water on the pipes but there were no signs of air leaks. Is there any advice that will help me I'm about to go nuts with this pool. Thank you in advance.