Compare Quick view Hayward HAYWARD | FILTER DE 48 SQFT NO VALVE | DE4820 MSRP: Was: Now: $932.73 HAYWARD | FILTER DE 48 SQFT NO VALVE | DE4820 Pro-Grid™ Vertical Grid ITEM # PROGRIDVG Description Diatomaceous earth is a porous powder with microscopic openingsthat when magnified look like tiny sponges...