Total Dissolved Solids

TDS is, as the name suggests, the sum of everything that is dissolved in the water including, minerals, chemicals and debris.  The maximum recommended T.D.S. level is 1,500mg/l, when the level rises above this it is time to do some dilution, by removing some of the old pool water and adding some fresh.

Regular backwashing of the filter as mentioned under Circulation and Filtration will mean that your pool will need topping up with fresh water fairly often, this will help keep the T.D.S. level under control and reduce the need to drain down and refill.