Total Dissolved Solids

Total Dissolved Solids (or TDS) refers to the total amount of anything in the pool water that is not water.  This includes any organic matter as well as any chemicals added to the pool to treat the organic matter.

If pool water is treated for conditions such as irritated eyes or skin while the pH level is good, or algae continues to bloom, or pool equipment and accessories continue to corrode while the pool water is balanced, the pool owner or service professional may need to look at the total dissolved solids as being the cause of such problems.  A certain amount of total dissolved solids is necessary for water balance, but a too high total of dissolved solids will interfere with the way chemicals added to the pool are supposed to do their job.  Every time chemicals are added to a pool, the total dissolved solids increase.  This includes chemicals used for sanitizing and balancing as well as algaecides and surface cleaners, pollutants, and oils and lotions brought into the pool water from bathers.  At a certain point, the level of total dissolved solids becomes too high to correct and the pool water must be drained and refilled with fresh swimming water, or drained partially and diluted with fresh water.