Reverse osmosis(RO) is a water filtration method to remove ions and molecules from water. By applying pressure on the one side of a membrane, pure water can cross the membrane but large molecules can not. 

Generally, molecules move from a region of higher concentration to a region of lower concentration. We call this phenomenon as Diffusion. Reverse osmosis occurs when molecules are moved through the membrane against the concentration gradient (Helmenstine, 2019). In other words, molecules are moved from lower-concentration region to higher-concentration region

Tiny pores in the membrane only allow pure water molecules to pass through while contaminants are blocked. In this case, clean and filtered water is separated from contaminated water.

Different reverse osmosis membranes adopts different micron sizes. A membrane with smaller micron size means greater precision, thus has greater filtration capability, than a larger one.

There is a common misconception about RO water, saying that RO water is too pure thus cannot meets human daily minerals intake requirement. It is undeniable that essential minerals are reduced together with the harmful contaminants during the RO filtration process. However, our daily access to these essential minerals are mainly dependent on food. And our bodies prefer natural organic minerals, which are only available in food. Besides, compared with the food, the amount of these mineral elements in water are quite limited and the quantity is too small to have an impact on health. On the other hand, water filter systems that do not remove minerals also leave more or less harmful contaminants in your water.

Hence, trust your RO water and say goodbye to bottled water!