The pool has a large suction at the beginning then dramatically drops to almost none. We have checked leaks in pipes,fittings,motor,o-rings, etc. When we checked for pipe leaks, I bought pipe to stick into pool to see if it would still have suction or none, when you add the hose plus cut off air it would prime no problem, drop it into the water and suction gone. Hook original pipe back up and still no suction. Put the sand filter on closed and it primes right up. I have no idea what is wrong and need any help I can get!