have had an extremely frustrated opening of pool this year....replaced liner, that was the easy part. Attached skimmer, pump, and filter hoses and everything seemed to be working....good flow in pump basket, great return..2 days later, sand in bottom of pool, unable to keep prime in pump basket, found out we had crossed hose leading from pump to multiport valve with hose leading to return...emptied sand, cleaned everything, took apart valve and still not able to keep prime. there are no leaks, all o-rings lubed, cannot figure out what the problem is now.