Thanks for these posts...

I'm starting my 4th season with a sand filter, and I was wondering the same thing. I noticed that this year it seemed to take longer to get the water clear, but it's crystal now - and everything seems to be working fine.

When I was backwashing while trying to clear the water, there was plenty of dirt that came out of the filter, and things seemed fine, but I also wondered about when to change the sand.

I have another question however: When it comes time to change the sand, what is the 'recommended' method. My plumbing is all glued to the valve head (on top of the filter - not the side) so it would seem to be very difficult to change the sand on mine.

Any pointers for future reference with regards to the plumbing being glued on.