Mineral or Demineralised Water: Which Is Right for You?

The difference lies in minerals and treatment

Mineral water contains dissolved minerals such as calcium and magnesium in amounts that vary by source and product. Demineralised water is treated—through processes such as reverse osmosis, distillation, or deionisation—to reduce most dissolved ions and minerals. Its TDS is therefore generally lower.

TDS, however, is not a health score. A low reading does not prove that water is free from microorganisms or every harmful chemical, while a higher reading does not automatically make water unhealthy. What matters is the actual composition, microbiological and chemical safety, process control, and fitness for the intended use.

Can both provide hydration?

Yes. For healthy people, safe mineral water and safe demineralised water both provide the fluid the body needs. There is no sound basis for general claims that demineralised water is always absorbed more easily, hydrates faster, pulls toxins from the body, or lightens the workload of healthy kidneys.

Minerals in water are not medicines, but calcium and magnesium in water can be absorbed and contribute to daily intake. The contribution varies by product, and food normally remains the main mineral source. Mineral or remineralised water can therefore be a rational everyday choice, while compliant demineralised water is not automatically harmful when the diet provides adequate nutrients.

Does long-term consumption of demineralised water cause mineral deficiency?

It is not accurate to say that demineralised water automatically causes mineral deficiency. Food remains the main source of calcium, magnesium, and other nutrients. Demineralised water, however, contributes little or none of these minerals. For people whose diet is already limited or whose calcium and magnesium intake is marginal, losing the contribution from drinking water may be an additional factor worth considering.

WHO notes that drinking water can contribute calcium and magnesium and may matter for people with marginal intake. Where a supply is demineralised, the water requires stabilisation before distribution, and restoring calcium and magnesium may be considered according to technical needs and local conditions. WHO has not set universal minimum mineral concentrations because adequate intake also depends on diet and other factors.

A responsible message is therefore not that demineralised water is inevitably harmful. The water should comply with applicable requirements, the system should remain controlled, the diet should provide adequate nutrients, and people with specific health needs should seek qualified advice.

Why can an electrolysis demonstration be misleading?

In some sales demonstrations, two electrodes are placed in water samples. Mineral water may turn brown, green, or dark, while RO or demineralised water remains relatively clear. The colour is then presented as evidence of ‘toxins’. That conclusion is not valid.

Dissolved minerals and salts allow water to conduct electricity more readily. When current flows, electrodes—particularly iron or aluminium ones—can oxidise or corrode. Material released from the electrodes can then form coloured oxides or hydroxides. Demineralised water conducts electricity far less effectively, so there is less reaction and electrode corrosion. Much of the colour and sediment may therefore be created during the demonstration rather than revealing a pre-existing load of toxins in the water.

Conductivity and TDS give only a general indication of dissolved ions. They do not identify whether those ions are ordinary calcium, sodium, nitrate, arsenic, or another substance. A sales electrolysis test is not a drinking-water safety test. Safety requires laboratory analysis of microbiological and chemical parameters selected for the source and intended use.

The purest-sounding water is not automatically best for every need

Very high purification can be valuable for specific industrial, laboratory, equipment, or source-water requirements. For drinking water, the final product must still be judged by safety, stability, taste, sanitation, and quality at the point of consumption—not merely by a technology's ability to lower TDS.

Very low-mineral water can taste flat and, depending on pH, alkalinity, and system conditions, may be more aggressive towards plumbing materials. Some systems therefore use controlled remineralisation or chemical adjustment to improve taste and stability. This must be properly designed and managed rather than used as a marketing label alone.

How should you choose?

For everyday use by a healthy person, choose water that is legally supplied, safe, hygienically treated and stored, and pleasant enough to support adequate drinking. Read the product category and label; do not judge quality only from words such as mineral, demineralised, RO, alkaline, mountain, or from one handheld-meter reading.

Medical needs cannot be generalised. People with kidney or heart disease, blood-pressure concerns, electrolyte disorders, or fluid restrictions need advice based on their diagnosis and test results. Demineralised water is also not automatically sterile or suitable for every medicine or infant formula; follow product directions and qualified health advice.

Indonesia treats mineral and demineralised water as different categories

Indonesia maintains separate standards for Mineral Water, Demineralised Water, and Natural Mineral Water. Ministry of Industry Regulation No. 62 of 2024 makes the relevant national standards mandatory for bottled drinking-water categories, including SNI 3553:2023 for Mineral Water, SNI 6241:2023 for Demineralised Water, and SNI 6242:2023 for Natural Mineral Water.

Different categories have different characteristics and processes, but each must comply with the requirements that apply to it. A logo, source story, treatment name, or TDS value does not replace process control, sanitary inspection, laboratory verification, and correct packaging handling.