Top Stuck on DE Filter

I have a Nautilis DE Filter that I need to clean inside and check the grids since I think I might have a tear (DE in pool). I shut the water flow, turned off the filter, drained the filter and took off the clamp but try as I might, the top will not come off (despite striking it around the top -- probably harder than the suggested direction :) ).

Any thoughts on what might be going on?

Thanks,

Andy

Andy, drain the water out of it, the vacuum from the water still being in the tank is what's preventing you from pulling the top off.:cool:

Waste:

Thanks for your reply. When I first posted, I had turned off all the water to the filter, opened the pressure valve and then opened up the drain at the bottom of the filter. Water ran out for quite some time but the top still didn't budge. I'm sure there's something else I'm doing wrong, but I don't know what it is.

Thanks,

Andy