Total Dissolved Solids are the total weight of all solids that are dissolved in a given volume of water, expressed in units of mg per volume of water (mg / L), also referred to as parts per million (PPM). The National Spa & Pool Institute recommends pool and spa TDS levels be maintained between 1,000 and 2,000 ppm not including salt.
Issues correlated with High TDS
Interferes with the normal workings of sanitizers by creating a protective barrier around bacteria, algae and other substances normally attacked by chlorine preventing sanitizer molecules from circulating freely.
Can cause eye and skin irritation
Can result in corrosion of metal equipment & accessories
Can permit algae to grow