What are Total Dissolved Solids (TDS) and How Do We Test for Them?

TDS is anything—other than the pure H2O—in water that you cannot see. This could include any salt, metal or mineral, and the lower the TDS level is, the purer the water. TDS is measured on a quantity scale, either in mg/L or, more commonly, in parts per million (ppm).

An elevated total dissolved solids concentration does not mean that the water is a health hazard but can result in your water having a bitter or salty taste; result in films, or precipitates and stains on fixtures; corrosion of fixtures, and reduced efficiency of water filter and equipment.