Most undercounter water filters have several cartridges to remove different types of contaminants. A carbon or activated carbon cartridge removes unpleasant odors and tastes, as well as reducing the water’s toxicity. A sediment filter is especially necessary if you have well water, and it is designed to remove tiny particles of rock, sand, and dirt that may have found their way into your water supply. We got ours from Better Water Store. A carbonyl cartridge targets iron and other metals in your water, as well as reducing any bitter tastes. We like our filter. It’s simple and easy to use and saves a lot of plastic water bottles.