Reverse osmosis (RO) water and distilled water are common terms for treated water, often causing confusion. While both processes aim to produce cleaner water by removing impurities, they employ distinct mechanisms and yield water with varying characteristics. This article clarifies whether RO and distilled water are the same and explores their unique attributes.
Understanding Reverse Osmosis
Reverse osmosis is a water purification process that uses a semi-permeable membrane to remove dissolved substances and contaminants. Pressure forces water through this membrane, allowing water molecules to pass while blocking larger impurities, which are flushed away. RO systems remove a wide range of contaminants, including dissolved salts, particles, colloids, organics, bacteria, viruses, pyrogens, lead, nitrates, pesticides, sulfates, fluoride, and heavy metals. However, RO systems typically do not remove dissolved gases well, such as carbon dioxide, because they have a low molecular weight.
Understanding Distillation
Distillation is a water purification method. The process involves heating water to its boiling point, causing it to vaporize into steam. As the water turns into steam, impurities like minerals, heavy metals, bacteria, and most chemicals are left behind. The steam is then collected and cooled in a separate condenser, where it reverts to its liquid form, resulting in purified water. This method is highly effective at removing nearly all dissolved solids.
Comparing Reverse Osmosis and Distilled Water
While both reverse osmosis and distillation produce purified water, their processes and resulting water quality exhibit notable distinctions. Reverse osmosis relies on pressure to push water through a membrane, physically separating contaminants based on size and charge. In contrast, distillation involves a phase change, where water is boiled into steam and then condensed, leaving impurities behind due to their different boiling points. Distillation generally achieves a higher level of purity, removing nearly all dissolved solids, often resulting in less than 1 part per million (PPM) of total dissolved solids (TDS). Standard reverse osmosis systems typically remove 95-99% of dissolved salts and other contaminants.
Regarding mineral content, both processes remove most naturally occurring minerals like calcium and magnesium. Distilled water is virtually devoid of all minerals, which can give it a “flat” or “bland” taste. Reverse osmosis water, while also low in minerals, may retain trace amounts, and some RO systems incorporate a remineralization stage to reintroduce beneficial minerals for improved taste. In terms of energy consumption, distillation is generally more energy-intensive due to the heat required to boil water. Reverse osmosis typically consumes less energy, as it relies on pressure rather than boiling, making it a more energy-efficient option.
Choosing the Right Water for Your Needs
The choice between reverse osmosis and distilled water often depends on the specific application. Distilled water’s extreme purity makes it ideal for uses where even trace minerals could cause issues. Common applications include scientific experiments, medical equipment sterilization, automotive cooling systems, and humidifiers, where mineral buildup can lead to damage. Its lack of minerals prevents scale formation in appliances and ensures no interference with sensitive processes.
Reverse osmosis water is popular for drinking and cooking due to its balance of purification and taste. Many find RO water more palatable than distilled water, especially when systems include remineralization filters. RO systems are also commonly used in aquariums and for preparing infant formula, offering a clean water source without the complete absence of all minerals. Ultimately, the “better” water depends on whether the priority is absolute purity for specialized uses or a balance of purification and taste for daily consumption.