What Are Total Dissolved Solids?


“Total Dissolved solids” refer to mobile charged ions including minerals, salts, metals, cations or anions dissolved in given volume of water. This includes anything present in water other than the pure water (H20) molecule and suspended solids. (Suspended solids are any particles/substances that are neither dissolved nor settled in the water, such as wood pulp.) TDS is expressed in units of mg per unit volume of water (mg/L), also referred to as parts per million (ppm).


 Working principal-
     A TDS meter is based on the Electrical Conductivity (EC) of water. Pure H20 has virtually zero conductivity. Conductivity is usually about 100 times the total cations or anions expressed as equivalents. TDS is calculated by converting the EC by a factor of 0.5 to 1.0 times the EC, depending upon the levels. Typically, the higher the level of EC, the higher the conversion factor to determine the TDS. While a TDS meter is based on conductivity, TDS and conductivity are not the same thing.

     High TDS results in undesirable taste which could be salty, bitter, or metallic. It could also indicate the presence of toxic minerals. The Environmental Protection Agency(EPA) recommended maximum level of TDS in water is 500mg/L (500ppm).