The majority of the TDS in ...

The majority of the TDS in the raw water will be chloride, which accounts for approximately 55% of the solids and it is this, which will dictate the level of TDS present in the water after it has been RO treated.  The remainder will be the sum of calcium, magnesium and sodium along with sulphate.  They used to have a limit of between 100-1000 ppm TDS although this may have altered.  The starting level is 44,000 ppm TDS of which chloride accounts for 24,000 ppm as chloride and 14,000 as sodium. For RO to reduce the TDS to 100 ppm it would reduce the chloride to 55 ppm while the sodium would be 32 ppm.  The level of 1000 would give 550 ppm of chloride and 320 ppm as sodium and the water would start to taste slightly salty and the water becomes more corrosive.  So it would be better to keep it