I remember when a neighbor family went to a lake with a sandy beach, Lake Spivey, for you Atlanta area residents of a certain age, and they came home with sand in their suits. The mother ran them through two warm rinses in the AMP, but they still had sand in them so she said she was just going to hang them out to dry and that they could shake the sand out of them when they were dry. I am sure subsequent loads had sand in the fabrics.