What Is the Difference Between Distilled Water and Tap Water?

Martijn van den Bogaart/CC-BY-SA 2.0

Tap water is directly supplied from the home faucet, while distilled water is water taken from any source that has gone through a distillation process. Tap water contains compounds, such as iron, chlorine, magnesium and natural minerals, that either are added by the public water system or have gotten in the water supply. Distilled water is in its purest form, with no bacteria or inorganic compounds.

The Environmental Protection Agency regulates the distribution and safety of drinking water. The agency conducts periodic pollutant-specific minimum testing of the public water systems to ensure that the water coming out of the faucets is safe for human consumption. Water contaminants, however, can still enter water supplies if the water travels through poorly maintained distribution systems or through human and animal activities.

Distilled water goes through the oldest form of water treatment and relies on evaporation to remove impurities in the water. The boiling process removes inorganic compounds, such as iron, lead, nitrate and calcium. While distilled water seems a safer choice compared to tap water, the rigid distillation process removes even the necessary nutrients present in drinking water, such as iron and sodium. The distillation process also does not remove organic compounds that have lower boiling points than water, such as benzene and toluene. If the water goes through the process without removing these compounds first, they contaminate the distilled water again.