The coconut shell activated carbon removes bad tastes and odors, while the ion exchange resin softens the water to prevent the build-up of limescale. This helps to increase your pets' water consumption and reduce the risk of urinary tract infections. Cats are picky when it comes to water, and certain tastes and odors can stop them from drinking. To ensure the water is fresh and clean in the fountain, replace the filter every 2-4 weeks.