Here's a question for those of you with experience with a pool
multi-port valve. I've been having a debate with a friend who
says you're only supposed to turn them in one direction otherwise
it will screw up the spider gasket that's at the bottom of the
valve. But I don't see how that can happen. The valve uses a
spring to push the disc inside down onto that spider gasket/seal.
To move the valve, you push the handle down, which moves the disk
up so you can rotate it. At that point, nothing is even touching
the gasket/seal, so I don't see how which direction you turn it
matters. I do see how if you try to turn it without pressing
the handle all the way down, that would rub against the gasket
and could dislodge it, screw it up, etc.

I've also seen threads about this online, with some alleged pool
experts also giving the "only turn it one way" advice. But the
manual for the valve says nothing. Nor is there any arrow or
indication of this issue on the valve itself.

Here's it the type of valve:


http://i45.tinypic.com/5xr582.jpg