I was told that my pool water was “old” and needed to be replaced.
I was having several issues with my water and got it tested at several local pool stores. Most of them repeated the same thing, that my water was “old” and needed to be dumped and replaced. I might not remember everything from high school science classes, but I do remember that water is H2O, and that the “O” does not stand for “old”. There is no such thing as “old” water. Water is a natural solvent, and that means that the longer that the same pool water has been in place, the more solids that are dissolved into it. Drought prone Southern California is hardly a place that can afford to have pool owners dumping tens of thousands of gallons of water down the sewer drain, so I started Pool Water Recycling.
Total Dissolved Solids (TDS) is a measure of everything that has ever dissolved in your swimming pool water. This includes minerals that come from your pool chemicals, such as calcium and sodium, and every other bit of dissolved dust, pollen, swimmer waste, algae remains – everything!
If your pool in Southern California is staying at a low TDS level through backwashing, that is not really backwashing, that is pool draining and refilling- not backwashing.
TDS naturally builds up in swimming pools, and in commercial pools using liquid chlorine, TDS can raise by several thousand ppm per year. Commercial pools that use Calcium Hypochlorite don’t have it any easier, because that byproduct is more calcium- the same major ingredient that makes up limestone! Outdoor pools with sand or DE filters that are backwashed frequently dilute the TDS level to a degree, but a normal level of backwashing will not dilute the water enough to keep the TDS levels from climbing. If your pool in Southern California is staying at a low TDS level through backwashing, that is not really backwashing, that is pool draining and refilling- not backwashing.
Distilled water has a TDS level of 0, drinking water has a TDS of around 500 ppm (although during the drought, I have seen it creep up to around 700 ppm with high calcium), and sea water can be as high as 35000, but what about pool water?