Last year I had sand in the bottom of the pool, so the end of last season, I dumped all the sand and inspected the laterals. They all looked good. The actual trunk (Astral-Pool calls it the "filter collector") that the laterals screw into did have a space in it and that could have been the problem. I replaced that piece but not the laterals because I did inspect them thoroughly twice and they were ok. So now once again I have sand in the bottom of the pool. Pretty sure it's filter sand and not dirt/sand blowing in from the yard. Could anything else in the filter allow sand into the pool? Could new sand have some dust, very small sand particles that have to work their way out?

When I put the sand back in the filter I made sure that none went into that trunk piece, I put a plastic bag over it with an elastic around it.