I noticed my pump making the wrong sound (tone seems to vary rather than a confident purr) and would not self prime. After leaving it running for 5 minutes, I turned it off. I dissembled the valve in front of the pump and with a garden hose filled the skimmer pipe with water. Re assemble valve and pump now primes and away we go. If I turn the pump off and leave it for 15 minutes, wrong noise and wont prime. I think I may have a cracked pipe or faulty seal at one of the elbow joins under ground. Apart from calling in a leak detector guy is there anything else I can do to try and fault find the problem ?