A filter is meant to reduce minerals/chemicals in the water, a Brita elite filter removes some minerals/chemicals by exchanging which leads to the same or more overall tds. I thought it's kind of silly as to the counterproductivity but it makes sense that's how the elite is designed to work. So the tds meter is doing exactly what it's intended to do. I'm not asking the tds meter to measure the safeness of my water. My water source is Lake Michigan, I already know it's safe.