Total dissolved solids (TDS)
The total concentration of everything dissolved in your pool water, minerals, salts, and chemical byproducts combined, measured in parts per million.
Total dissolved solids (TDS) is a single number representing every dissolved substance in the water: calcium, chlorine byproducts, dirt, sunscreen, salt (in saltwater pools), and more, all combined. It naturally climbs over a season as chemicals are added and water evaporates, concentrating what's left behind. High TDS doesn't cause a specific symptom on its own, but it can make water balance harder to manage and, at high enough levels, dull water clarity and reduce chlorine's effectiveness. The usual fix once TDS climbs too high (often 2,500-3,000+ ppm) is a partial drain-and-refill to dilute it back down.
Track this with Skimmer — log water tests and keep every reading in one place.
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