Reverse Osmosis (RO) and distillation are two popular methods for purifying water. While both processes aim to significantly reduce contaminants, they achieve this through entirely distinct physical principles. Understanding how each method works is the first step toward clarifying whether they produce the same final product. The core difference lies in whether the water is forced through a physical barrier or whether it is changed into a gaseous state and back again.
Understanding the Reverse Osmosis Process
Reverse Osmosis relies on mechanical filtration to purify water. It involves applying significant pressure to the source water, forcing it through a specialized semi-permeable membrane. This membrane acts like an ultra-fine filter, designed with pores small enough to allow water molecules to pass through while physically blocking larger contaminants.
RO effectively separates water from dissolved solids and salts, which are rejected by the membrane and flushed away in a separate waste stream. This system is highly effective at removing a wide range of impurities, including heavy metals, salts, and bacteria, often achieving a contaminant rejection rate of 90% to 99% of dissolved substances. The final product is known as permeate, which is highly purified filtered water.
Understanding the Distillation Process
Distillation is a purification method based on a thermodynamic phase change. The process begins by heating the source water until it reaches its boiling point. As the water turns into steam, it leaves behind any substance that has a higher boiling point than water.
The resulting water vapor is then directed into a cooling chamber, known as a condenser, where it is cooled back down into liquid water and collected. Non-volatile contaminants like minerals, salts, and heavy metals are unable to vaporize, so they are left behind in the boiling chamber. This method achieves an extremely high level of purity, resulting in water that is nearly 100% pure H₂O. However, substances with a low boiling point, such as certain volatile organic compounds (VOCs), may vaporize and carry over into the final product unless post-filtration is utilized.
How the Final Water Products Compare
The answer to whether reverse osmosis makes distilled water is no, because the underlying mechanism and the resulting purity profile are fundamentally different. RO water is highly purified filtered water, while distilled water is highly purified condensed water resulting from a phase-change process.
A key metric for comparison is the level of Total Dissolved Solids (TDS), which measures the concentration of dissolved substances. Distilled water is created by separating the water molecules completely from all dissolved solids, typically resulting in a TDS reading of zero or near-zero parts per million (ppm). RO systems are excellent at contaminant removal but typically remove 90% to 99% of TDS, meaning the final product can retain a small, measurable amount of dissolved solids.
The processes also differ in how they handle volatile chemicals. Distillation, while superb at removing non-volatile solids, can allow some VOCs to carry over with the steam, a problem often mitigated by incorporating an activated carbon filter at the end. Conversely, a standard multi-stage RO system, which typically includes an activated carbon pre-filter, is highly effective at removing VOCs before the water even reaches the membrane.