TDS (total dissolved solids)

TDS — total dissolved solids — is a single figure (in parts per million, ppm) for how much dissolved mineral, salt and metal is carried in water, usually read with a cheap handheld meter. It doesn't tell you *what* is dissolved or whether water is safe — it's an indicator, not a safety test — but it's a useful everyday gauge. In the UAE most mains water starts from desalination and is treated to a safe, relatively low TDS, but by the time it has sat in a rooftop or underground storage tank and run through building pipes it can pick up hardness and taste. A high TDS tends to track with the hard-water problems Dubai homes know well — limescale and descaling on heaters, kettles and mixers, spotting on glass, and shortened appliance life. TDS is also how you check an RO (reverse-osmosis) filter is working: measure before and after the membrane, and a big drop means it's doing its job (a small drop means the membrane is spent). Very *low* TDS isn't automatically 'better' — RO strips beneficial minerals too — so the goal is sensible, not zero. Because a lot of taste and scale complaints trace back to the stored supply, pairing a filter with periodic water tank cleaning in Dubai is what actually fixes them, not the meter reading alone.