Why is Total Dissolved Solids important ?
Total Dissolved Solids (TDS) is simply a measure of the total amount of dissolved material in the water. The TDS in the pool is influenced by many factors; the chemicals we add to adjust the pH, chlorine, water hardness, alkalinity, dust, dirt and debris. The maximum acceptable level of TDS for pools is 1,500 ppm. Above this level there is risk of staining of pool surfaces, and high TDS will also reduce the activity of any treatment chemicals you add; the pool water may become cloudy. The only practical solution is to drain some or all of the water from the pool and to replace it with fresh water (with a low TDS). You should seek the advice of a pool engineer before draining an in-ground swimming pool. A regular backwashing routine will help to prevent high TDS.
