The common perception that filtered water and distilled water are interchangeable often leads to confusion. Both methods aim to purify water, yet they achieve this through distinct processes and result in different levels of purity. Understanding these differences is important for choosing the appropriate water for various uses, from drinking to specialized applications.
How Water is Filtered
Water filtration involves passing water through a physical or chemical barrier to reduce contaminants. Common methods include activated carbon, reverse osmosis, mechanical filters, and ultraviolet (UV) systems. Activated carbon filters absorb chemicals like chlorine, pesticides, and volatile organic compounds (VOCs), improving taste and odor. Mechanical filters remove larger physical particles such as sediment, dirt, and silt.
Reverse osmosis (RO) systems utilize a semi-permeable membrane to remove a wide range of dissolved solids, including salts, heavy metals like lead, nitrates, and some bacteria and viruses, by forcing water through tiny pores under pressure. RO systems often incorporate sediment and carbon filters as part of a multi-stage process. UV filtration uses ultraviolet light to destroy bacteria, viruses, and other microorganisms. Filtration processes remove harmful substances while often retaining some beneficial minerals. The specific contaminants removed depend on the filter type and quality.
How Water is Distilled
Water distillation is a purification method that mimics the natural water cycle, involving a phase change. The process begins by heating water in a boiling chamber until it vaporizes into steam. As water turns to steam, almost all impurities, including dissolved minerals like calcium and magnesium, salts, and heavy metals, are left behind. The intense heat also inactivates microorganisms such as bacteria, viruses, and protozoan cysts.
The steam then rises and enters a separate cooling section, typically containing condenser coils, where it is cooled. The steam condenses back into pure liquid water, which is then collected. This results in highly pure water, often cited as 99.99% pure, with virtually no dissolved solids. Some volatile organic compounds with boiling points similar to or lower than water might vaporize and condense, sometimes necessitating additional filtration.
Comparing Filtered and Distilled Water
The primary distinction between filtered and distilled water lies in their purification processes and resulting purity levels. Filtered water, depending on the filter type, removes various impurities like sediment, chlorine, and certain heavy metals, but often retains dissolved minerals. Distillation effectively removes almost all impurities, including dissolved minerals, salts, and microorganisms, by boiling and re-condensing the water. This makes distilled water significantly purer, with a total dissolved solids (TDS) content often below 1 part per million (PPM).
The absence of minerals in distilled water can affect its taste, often described as “flat” or “bland,” as minerals contribute to water’s flavor. Filtered water, retaining some natural minerals, typically has a more familiar taste. Due to its high purity, distilled water is specified for applications where mineral buildup or chemical reactions from impurities are undesirable. This includes medical equipment like CPAP machines, laboratory experiments, car batteries, and steam irons.
Filtered water is commonly used for everyday drinking, cooking, and general household purposes, as it provides cleaner water while often retaining beneficial minerals. Filtered water is generally preferred for daily consumption due to its mineral content and taste, while distilled water is reserved for specialized needs requiring ultra-purity.