I have been reading the forums and see some similar issues but not quite what I am seeing.
Turn on system (1 1/2 pump, sand filter, both Hayward) Pressure is at around 15/16, water flow is nice and strong. After about 30-40 minutes pressure starts creeping up and flow gets lower. 90 minutes later pressure over 20, flow almost not existent. Back washings seems to "reset" the cycle.. but same thing happens.
First thing that came to my mind was a suction side air leak... but the the pump basket is completely full.. no bubbles or anything just clear water. I have reconnected all hoses.. nice and tight no leaks there ( i even lit some inssense to see of i could get some smoke to pull to the suction..nothing). When i attempt to vaccum the pool.. i lose all suction with in 5 - 10 minutes.
I am hoping one of you have some suggestions as I am at wits end and the wife is saying to just put the winter cover back on and scratch the season as a loss.