What grade of sand to use for pool filter?

.017 to .022 silca sand found at any pool supply store New: I doubt that you are going to find .017 or .022 sand even at a building supply place that specializes in sand, plaster, rocks, gravel etc. A #20 silica sand is what is available for swimming pool filters and that is what should be used. .017 sand may in fact be too small for the latterals in a sand filter thus letting small amounts of sand to pass thru to the pool daily resulting in a buildup of dust and sand on the floor of your pool.