Every two to four weeks for the carbon element, and rinse the foam pre-filter weekly — the foam protects the pump and is washable, which is why half the replacement packs sold contain something you did not need.
Two components, two schedules, and only one of them is a consumable.
The foam pre-filter
Catches hair and grit before the impeller. Rinse it under the tap weekly. It lasts several months and it is what keeps the pump alive.
The carbon pad
Handles taste and smell, and is spent after two to four weeks whatever it looks like. Carbon gives no visual warning.
In a moulting household
Hair loads the pre-filter far faster than the calendar suggests. Look at it rather than at the date.
Generic versus original
On the Catit Flower range, third-party pads are usually dimensionally identical. Elsewhere, a filter that does not seal lets water pass round the edge, which is the same as no filter at all — test one pack before buying several.
Last reviewed 2026-08-17