Filtration Media: KDF and Chlorgon. KDF is a patented specialty medium used in most shower filters and in other water filtration venues. Chlorgon is a patented special filter medium unique to Sprite products. The cartridge is reversible. It can be easily rotated to operate in either direction. Although rotating the cartridge is not necessary, and many users don’t bother, periodically reversing the cartridge backwashes the cartridge as it is filtering, ensures balanced filtration, reduces the likelihood of channeling, and should prolong the life of the cartridge. The manufacturer recommends monthly reversal of the cartridge.