Why is sand flowing into my pool and how do I fix it?

Sand flowing into the pool is typically caused by sand that is too small, a sand level that is too high, or a broken skimmer. Use only recommended #20 silica sand (0.45–0.85mm), ensure the sand level is between the MAX and MIN marks on the collector hub, and replace the skimmer if broken. Always stop the sand filter before changing the control valve position. (Page 9)