Leaking Multiport valve (?) questions

[bbodb1]

Good morning all.

I woke up this morning to a lower than expected pool level and later discovered that while the pool pump was a running, a slow trickle of water was running out the exhaust line (the same line where water would run if I were backwashing the pool). The attachment Pump Setup shows where the leaking water was found (see Leaking Exhaust). Again, it was a very slow yet steady trickle of water. I observed this area multiple times over several minutes and each time I witnessed the same amount of water being discharged at a very similar rate.

It has been quite some time since we have opened the Multiport valve for any reason (certainly more than 5 years and perhaps as long as 10 years - maybe longer) and we cannot recall if this valve has ever been replaced.

With this in mind (and wanting to stop the leak), I plan on opening the multiport valve to ensure nothing foreign has become lodged in the multiport valve itself.

I did search a bit around here and did find someone with a similar problem in the past - see this thread so I will be taking the top of the multiport valve off next.

...more to follow...including more photos...

 

[bbodb1]

Now with the multiport valve open, I am hoping this leak can be explained by the missing portion of the gasket in the attached photo. Is this a reasonable guess?

While I have the multiport valve open, I'll definitely clean this out / up a bit.
The O ring seemed to be fine (still very flexible, easy to remove, no decay of the ring noted, etc) but would I be correct to put some sort of lubricant on it since I already have access to the O ring?

 

[bbodb1]

Another view of the inside of the multiport valve along with a view of the bottom of the multiport cover (that is the gray item).

 

[sande005]

Now with the multiport valve open, I am hoping this leak can be explained by the missing portion of the gasket in the attached photo. Is this a reasonable guess?

While I have the multiport valve open, I'll definitely clean this out / up a bit.
The O ring seemed to be fine (still very flexible, easy to remove, no decay of the ring noted, etc) but would I be correct to put some sort of lubricant on it since I already have access to the O ring?

Not a guess - that is defiantly the source of your issue. Easy to replace, and lube it up like an o-ring when putting the new one in. Magic Lube in the red tube, or similar pure silicone. Not the kind with teflon. Most pool stores will have both. Get a new main o-ring too, just cause it may be another 10 years before you look at it again.
Besides just getting old, the biggest cause of this kind of problem is moving the multi-port valve when there is still pressure. Always turn the pump completely off before moving the handle.
Since you have it open, look at the handle assembly also. There is usually a big nylon type washer that can get chewed up over time, so might as well replace that too. Will greatly improve the ease of changing positions.

 

[bbodb1]

On the possibility this thread may serve of use to others later, the photo attached here shows inside the multiport valve (and the underside of the cover plate) AFTER the removal of the spider gasket.
Based on what I was reading elsewhere, I was lucky in that the gasket pretty much came out in one piece. Unsurprisingly, the gasket was dirty (my hands had black stuff all over them) and had a grimy (sandy) feel after removal.

The o-ring was in much better shape and while it too left some black marks on my hands, the o-ring felt flexible to the touch.

 

[bbodb1]

Inside surfaces of multiport valve cleaned about as well as we can.
Waiting now for delivery of parts....