Replace when the water is no longer colored.
BLOCK,RIM HNGR,NONPARA BIG D TOILET BOWL RIM HANGERS WITH NON-PARA BLOCK fit most toilets and deodorize up to 1,500 flushes 30 days normal operation. The compound inside gradually dissolves, coloring the standing bowl water a fresh aqua as it imparts a nice fragrance. Blocks are acid-free and water-soluble.Deodorizer Type: Toilet Bowl Block; Scent: Evergreen; Colors: White.