Question: is tds the same as hardness?
Answer: There is not much of a difference between hardness and TDS of water. ... The higher the level of TDS (ppm), the higher the degree of hardness. Water hardness is typically reported in grains per gallon, milligrams per liter (mg/l) or parts per million (ppm). One grain of hardness equals approximately 17.1 ppm (mg/L) in TDS.