Yes I have used them. Claude Leval invented them years ago. They worked for coarser sand quite well. But again, the flow rate really had a lot to do with it. He made many different sizes of them to compensate for water flow and pipe sizes. I used a couple of them with success and then tried one on a well which had very fine sand. That sand went right through like the separator wasn't even there.

Sand is a big problem with well water. It can clog plumbing, it can ruin pump impellers and eventually shut off your water if there is enough of it. The best fix is to try and repair the well or install a new one.