Bought several online shower filters over the last twenty years or so.Because of car troubles I shop more and more online. The last thing I bought at a regular store was groceries, not going to list every one of them, too tired right now. The last thing I bought online was Sage shampoo on Amazon. It's very good for an itchy scalp.
It helps reduce itchy scalp and itchy skin because it takes out most of the chemicals in the tap/shower water that cause problems.
Last I checked, a five or eight stage filter, including vit c stage, was only about twenty green pieces of paper. :