950 # of sand????? are you sure? I have a 20" filter and it uses 200#.

Update: I checked Pentair's web site and a 36" does take 925 # of sand--and is appropriate for a pool with between 67,000 and 101,000 gallons! The BIGGEST home pools here we see are in the 40's... Is your pool that big?

Saying that, I'll bet ANYTHING your multivalve is bad, not your sand. It's POSSIBLE the laterals in the filter have broken as well. If you don't get a release when you push down, something is definitely wrong.

So, from what I can glean sand is not likely your problem. Something else is.