Water Filter (Kashering) Status: The pitcher should be cleaned well on the inside and outside, because it is used all year round at meals where chametz is served. It is commendable to use a new filter cartridge for Pesach. [Placing your chametz cartridge in water for Pesach will allow you to reuse it after Pesach.] Assuming you never wash it with hot water, there is no need for a hot kashering of the pitcher.