Sand in my pool?

[Poconos]

Ed,
Welcome to the forum. If there is sand in the pipes it will get blown out fast so this is not why the stuff keeps coming back. The only way I can think of something that you put in getting blown back to the pool is if you did it with the valve set to Backwash then did not do a Rinse before switching to Filter. Are you sure the stuff in the pool is sand? Can be confusing sometimes. If the stuff gets kicked up very easily it could be silt, pollen, or any fine stuff the filter won't catch. Filter sand will definitely be gritty. Check these things and post back. we'll eventually figure what's going on.
Al
Edit: Some on this forum recommend all sorts of maintenance things for sand filters. Using cleaners, tearing apart, washing, etc. I'm on my 9th season with a 300# Hayward sand filter and do nothing but backwash when needed and add a little DE powder after a backwash to assist in filtering smaller stuff. Sand filters are the easiest and cheapest to maintain.