Hayward filter valve removal

[Done487]

I'm trying to narrow down the cause of a sudden rise in pressure (even after a good backflush). I suspect contamination on the filter bed. I found what looks like gooey thick slimy material in the strainer basket. I'm thinking this may be what has clogged the sand (what the heck is it, where did it come from?). So, I want to remove the valve head assembly so I can get to the sand, thinking I can replace the top layer of sand. My filter is hard piped to the return, pump, discharge. My question is; can I remove the collar and slide the filter out from under the valve assembly? Has anyone done this "manuever", if so what tips can you give me? Thanks