Through a series of events that I won't get into, I ended up changing the sand in my filter last night. When I pulled the valve body off the filter housing, the stand pipe came up with it. I managed to get the two seperated, and found that quite a bit of sand had found it's way in between the stand pipe and the hole it fits into (which is why the stand pipe pulled up). I finally got the sand and all the internal parts out, then cleaned/inspected everything. Appearantly no damage was done to the laterals or anything else. My question is, how did the sand get in between the pipe and valve body? The spider gasket looked fine as far as I could tell. Should I replace it anyway?