There wasn't much of a chance to get the orientation of the new valve wrong. Though I didn't work to try putting it on backwards, its the same orientation as the one that came off it.

Overfilled with sand is a consideration. I've been resisting pulling the rest of the top off because of the plumbing (much would have to be replaced). I think the fixed gasket would create a difference in pressure as the filter sees it (old pressure gauge was out as well, so can't tell a before/after pressure).

Sounds like I might have to bite the bullet and yank the top off the filter to check deeper.

One thing that's tough with this setup is that I don't really have a known good working state to start from. When we bought the house I could tell the old gasket was already bypassing to waste (water missing from pool) or recirc (tough time cleaning). Now that the valve/gasket has been replaced, there could be any number of issues that present when they wouldn't have before.