Total Dissolved Solids (TDS) is the measure of the total of all the soluble substances dissolved in the water.
For swimming pools, the maximum recommended TDS level is 1,500 ppm. Values above this can lead to various problems with your pool. Some of the issues include: cloudy pool water, staining of the pool surfaces, scaling, hard water, a salty taste, algae growth and irritated skin and eyes.
In swimming pools using salt-chlorine generators, the large volume of salt added radically increase the TDS level. Sunscreen, sweat, debris and other chemicals also increase the TDS level and create a residue in your pool.
The TDS should be checked once every six months. If the pool water has become saturated with contaminants and the TDS level confirms this, the pool should ideally be drained and refilled with fresh water. There is no method to reduce TDS effectively without replacing some or all of the swimming pool water.