I recently changed the sand on my hayward S244T filter and now it's putting sand back into pool after backwashing and rinsing. I was very careful with the standpipe and laterals during the change out. I filled the filter about 1/2 full with water prior to adding sand slowly and carefully so I don't think lateral damage is the culprit. I have read a lot about sand in the sightglass during the backwash cycle but I don't see any sand in my sightglass until I switch to rinse.