Welcome to the Forum!

Glad you were able to find good advice to help you. As long as you're trying the gasket first, try it without gluing or siliconing it down Al (Poconos) and I had a discussion about this a few years ago and I still say I never had a problem not securing the gasket in place, as long as the channels it sits in are in good shape. If you glue it in and the channels are shot, you'll ~ wreck the gasket trying to peel it back out. If no glue doesn't solve the problem, then by all means put some glue or silicon on it and try again. If that still doesn't work, it's time for a new multiport valve. [I don't seem to be able to get the advanced search function to work for me...???]

If you don't remember a double section being blocked off, you may have the older 6- spoke gasket (as opposed to the newer 5 spoke gaskets) - double check before getting the new one, as the part # you're looking for is the same for both the 5 and 6 spoke gasket. The part # is SPX710D for multiports with 1 1/2" piping and SPX715D for multiports with 2" piping.

One last thing, when you put the multi back together you'll notice that there is a flat (vertically) side to one of the 1/2 moon protrusions where the screws go on both the body of the valve and the top plate - be sure they match up! so that the valve is oriented properly.

Please let us know how things work out for you and feel free to ask any more questions you have.