1. “Dissolved solids” refer to any minerals, salts, metals, cations or anions dissolved in 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.)
2. In general, the total dissolved solids concentration is the sum of the cations (positively charged) and anions (negatively charged) ions in the water.
3. Parts per Million (ppm) is the weight-to-weight ratio of any ion to water.
4. Conductivity is usually about 100 times the total cations or anions expressed as equivalents. Total dissolved solids (TDS) in ppm usually ranges from 0.5 to 1.0 times the electrical conductivity.