Tagelus diverter / spider gasket

[Poconos]

In the rinse mode you would have a siphon going. Skimmer to pump to filter to waste line.
In the filter position that waste line should be totally blocked. Put it in that position and with the pump off try blowing into the waste line and see if you can move air. If you can then something is leaking which I suspect. Sounds like you can take that valve off easily so you may take it off and blow in the various ports to help isolate the problem. In filter mode, waste port blocked. Rinse, backwash, and waste positions, outlet to return line blocked. If you had it plumbed wrong you would have major problems, not these subtle things. This problem will be solved eventually. Keep at it.
Al

[RobDHW]

I agree with all you've said Poconos. As I remember, a few years back a local pool company was trying to figure out a problem we had & they "couldn't". I think they were pressure testing the lines & their readings weren't making sense. I know that a skimmer was "moved" long before we bought the house. The former owner and former pool company were useless. short of ripping up the yard, I'm think I'm stuck w/ the way it is, at least until the filter dies, or we get an underground leak (knock wood - I hope that's decades from now). Thanks for confirming what I've always suspected : our pool was plumbed by Mario & Luigi... the Mario Bros.

[Watermom]

Rob -- I just had to tell you --- I am the one who moderated your post in after you posted and when I read it, your last comment made me laugh! Thanks for the chuckle. That was great!

[RobDHW]

Glad that it got the desired effect. Gotta have a sense of humor...

[RobDHW]

Just as an FYI - I just backwashed my filter and left the pump off, but w/ the multi-port set to "filter". My backwash hose fills up to the return pipe level. I never did get around to blowing into it, but now I think I don't have to. Seems like a bad multi-port to me. Guess I'll be replacing that sometime.... Right now it's not causing me enough grief to spend the time & effort.

-Rob

[RobDHW]

I finally got around to blowing into the waste line. I think I moved water, although if it was from the skimmer or return I'm not sure. I might mess with it over the weekend, but I'm inclined to think that I'll really work on it when I close the pool in the fall. Taking the multi-port off the filter is not easy, do to the way I've replaced some PVC, so I'd just as soon do that over correctly at the same time. Once i've got it open I'll probably change the sand & check the laterals too. Thanks all for your help. I love the fact that I'm not scared of my pool stuff any more and really understand how it works.
-Rob