Faulty Multiport Valve? Water back to pool when pump off

[dvmdoc]

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?
Thanks-
Warren
Toms River NJ

 

[Bama Rambler]

Sounds like you need to rebuild the multiport valve. How old is that valve?

Does the sight glass have a vacuum relief built in? Mine does.

 

[dvmdoc]

Sounds like you need to rebuild the multiport valve. How old is that valve?

Does the sight glass have a vacuum relief built in? Mine does.

Unknown how old the MPV is....I've owned the house 4 years...it has to be maybe 7-10yo, possibly older?
I'd had it apart over the winter mainly b/c I wanted to see how it worked inside and to lubricate any parts and was surprised how 'simple' it seemed inside but there's obviously something failing.
The sight glass does not have a vacuum relief built in so far as I can tell.

 

[Bama Rambler]

Did you lube it good when you put it back together?

I'd probably just rebuild it. It could be leaking at the valve stem seals.

 

[Smykowski]

Sounds like a spider valve gasket failure. I second the rebuild suggestion.

 

[Bama Rambler]

You can search for Hayward SP710 parts and you'll find the parts you need.

 

[dvmdoc]

OK, so I replaced the spider gasket (took out the old one, had the pool store glue in the new one). Everything runs great however when I shut off the pump I can still hear a suction leak sound coming from somewhere in the multiport. I haven't yet put a check valve on the 'waste' opening of the MPV. If the system is off for several hours then eventually I'll have air in my pump filter basket again.
Tonight, after vacuuming the pool I wanted to empty the pump filter basket. So I turn off the pump and with the MPV still in the 'filter' position I open the lid of the filter basket. Immediately there is a gurgling sound coming from the big DE drum and there is suction pressure that drains out the filter basket and draws air into the MPV/filter. Should I set the MPV to 'recirculate' to take the filter out of the equation when opening the lid of the filter basket or does this indicate some other problem and shouldn't happen?
Thanks-
Warren

 

[duraleigh]

I would locate that air leak in the multiport. Something often helpful is to take a piece of pipe (pvc works well) about 1" in diameter and place it to your ear and then locate the other end at suspect points on the multiport.....sort of like a redneck stethoscope.

That has worked for me more than once. If you can pinpoint and fix that leak first, you may not have to look any further.

 

[Bama Rambler]

A screwdriver also works well as a stethoscope. Just be sure to stick the handle end to your ear and not the blade end!

 

[dvmdoc]

A screwdriver also works well as a stethoscope. Just be sure to stick the handle end to your ear and not the blade end!

Thanks - you guys are great (speaking as someone from the medical community LOL!)
On a leak hunt....