PetSafe’s guidance is on the pack and depends on the number of cats — crystals dry solids rather than clumping them, so the tray is changed on a schedule rather than scooped.
Crystal systems work on a different rhythm from clumping ones.
How it behaves
Urine is absorbed and evaporates; solids dry out and are raked aside. Nothing is removed until the whole tray is changed.
What decides the interval
The number of cats, principally. Manufacturer guidance assumes one; two cats halve it, as with every capacity figure in this category.
The visible sign
Crystals darken as they load. That is a more reliable guide than smell, which your nose adapts to.
The cost question
Crystals plus trays is the most expensive way to run a litter box, and the reusable tray is the cheaper route within the same system.
Last reviewed 2026-08-17