Hayward Superpump through 2" Side-mount multiport valve (MPV) into DE filter.
With pump primed all is good no leaks noted nor bubbles in pump basket window.
Upon turning off pump (filter setting on MPV), there's an audible 'gurgle' as the water drains down the vertical clear connection between the pump and the MPV and eventually air gets in the pump filter chamber and back out into the skimmer lines (so it takes a bit to prime again when you turn it back on). All this happens in may 60-90s. There is no check valve between the pump and the pool.
After lurking around on this site (very helpful) I noticed that after I turn off the pump, there is a vacuum effect from the "waste" port on the MPV. I went ahead and plugged the waste port temporarily with a screw-in style wall return plug and this drastically reduced but not quite eliminate the problem.
Now when I turn off the pump I can hear a faint 'hiss' of air leaking into the MPV somehow but I can't locate it (is it within? from spyglass? from edges of mpv due to bad seal/gasket?). I'm comfortable taking things apart but don't know where/what step I should do next? I suppose the easy thing first and reseal/seat the spyglass but if that doesn't fix it what should I be doing or looking for?
Toms River NJ