Understanding hard water

Water becomes “hard” when it picks up dissolved calcium and magnesium as it passes through rock and soil. Hardness is measured in parts per million (ppm); water above roughly 200 ppm usually causes visible scale and soap problems.

The minerals are not usually harmful to drink, but when hard water is heated or evaporates they leave scale behind — on taps, tiles, geysers, pipes and the inside of appliances.

Diagram of a water softener connected to a home’s sump, overhead tank and taps

The ion-exchange process, step by step

  1. Hard water enters

    Water from your sump or borewell flows into the resin tank.

  2. Resin captures minerals

    Resin beads hold calcium and magnesium ions and release sodium ions in exchange.

  3. Soft water flows out

    Softened water goes to every tap, shower and appliance in the house.

  4. Brine recharge

    When the resin is saturated, a salt brine wash flushes the minerals away and the cycle starts again.

Problems caused by hard water

  • Poor lather

    Soap and shampoo do not foam properly, so you use more and still feel less clean.

  • Dry skin and dull hair

    Soap residue that will not rinse off can leave skin dry and itchy and hair rough.

  • Scaled geysers

    Scale insulates heating elements, so geysers take longer and use more power.

  • Spotted vessels and tiles

    White marks on steel vessels, glasses, taps and bathroom tiles.

Read: common signs of hard water · See our water softeners

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