In July 2014 I replaced the original pump (20+ years old, noisy and leaking) with a new identical pump, a Hayward SP2607X10 Super Pump 1-HP. Worked fine for the past 3 pool seasons. I've got my pool open this season but both the suction and output of my pump is really poor. I can't open both skimmers otherwise there is no skimming action. I've closed off one skimmer with a gizmo and shut the main drain and get OK skimming action. The two water returns... the volume of water is really poor. I can so easily cover a return with my finger. It wasn't like this last year, two skimmers and the main drain open...great skimming action. Covering a eyeball return was a hard thing to do, very powerful output. I checked the voltage at the pump plug, it's fine that's not the problem. Looking at the water in the pump basket, listening to the pump/filter...all seems OK. Could the impeller be slipping on the shaft? I'm not really sure how to trouble shoot this, comments/suggestions welcome.