Distilled water is essentially chemically pure water that contains almost no ionic impurities but may contain gases such as oxygen, nitrogen, and carbon dioxide. The electrical conductivity of distilled water is about 5 µS/cm.

Where is distilled water used?

Distilled water is used in chemical technology, the pharmaceutical industry, and the food industry. For household applications, it is mainly used for car maintenance and sometimes for humidifiers and irons. It is rarely used for drinking or cooking due to its specific taste caused by low mineralization.

Properties of distilled water

• Electrical conductivity: 5–10 µS/cm
• Mineralization (TDS): Less than 5 mg/L
• Acidity (pH): 5.4–6.6 due to dissolved carbon dioxide

How is distilled water made?

For producing distilled water, distillers are used. The principle of operation is based on heating water to a vapor state, then condensing it back into liquid form.

A distiller consists of a heating chamber (usually with an electric heating element), a cylindrical condenser to cool and condense the steam, and a collection container for the purified water.

Most household distillers use an electric heating element, though some models use gas heating, which is more complex and may pose a burn risk.

The diagram below shows a basic electric distiller. Water is heated in a lower chamber, turns into steam, and travels through a glass or metal condenser tube, where it cools and drips into a collection container. The remaining water in the heating chamber contains dissolved salts and impurities.

To obtain higher-purity distillate, the process can be repeated with the pre-purified water. Regular maintenance, including descaling the chamber and condenser, is necessary for proper operation.

Is distilled water really the purest?

No, its electrical conductivity can reach 5 µS/cm, while electrodeionization can reduce this to below 0.05 µS/cm. Reverse osmosis can also produce water with similar conductivity, but with lower energy consumption and greater safety in use.

Is distilled water harmful?

Distilled water is not harmful, but it does not provide any health benefits either. It lacks essential minerals, but if the alternative is low-quality surface or tap water, distilled water is definitely the better choice.

The World Health Organization (WHO) provides guidelines for biologically complete drinking water, but there is no mention of distilled water being harmful.