The CatGenie Washable Granules will never need replacement but you will need to add additional granules when the level of the granules fall below the line on the bowl. On average you will need to add a few cups a month and a box of granules should last between 4-6 months depending on the number of cats that use the CatGenie. The plastic in the CatGenie Washable Granules has been specially formulated to completely biodegrade in your sewer or septic system in about 9 months or less.
