What can a high TDS reading indicate?

High TDS levels may reveal the possible presence of toxic substances such as lead, arsenic, nitrate and more nasty stuff. It can also lead to water tasting salty, bitter or metallic. And it indicates the water may be ‘hard’, containing high amounts of calcium and magnesium, which can discolor plates and glasses as well as cause damage to dishwashers, washing machines and coffee makers, for example.