Reverse osmosis water filter works by forcing the water to pass through the membrane and the unwanted substances are flushed out using the unprocessed water and diverted to the drain. In other words, the water are forced through a 0.0001 micron semi-permeable membrane by applying high pressure. The membranes are usually a long sheets of membrane  rolled up around a hollow tube in a spiral way. This is referred to as a spiral membrane or also called a module. The size of the module is normally about 2 inches in diameter and about 10 inches in length.

The membrane is normally housed  in a membrane housing or a container. And when pressure is applied, the water are forced through the membrane filtering out any unwanted substances. The unwanted substances are then diverted and flushed out of the reverse osmosis water filter. This will prevent any unwanted substances from accumulating in the filter and clog up the membrane which will compromise the quality of the filtered water. This is the advantage of this water filter compared to other conventional water filters. This is also the reason why reverse osmosis water filter can last longer and function well with minimum maintenance.

All reverse osmosis water filters work the same way and may look alike to some extend. They usually have the same basic components. The main difference is the quality of the membrane used and this will determine the quality of the filtered water. Reverse osmosis water filter usually has carbon pre-filters to filter out chlorine to protect the membrane as membrane in the reverse osmosis water filter can be damaged by chlorine.

The basic process of a reverse osmosis water filter is as follow:

Reverse osmosis water filter pre-filtration

This first step of water purification process is where large particles and unwanted substances or impurities are removed from the water. The pre-filter is a carbon filter or activated carbon-based filter to protect the semi-permeable membrane and need to be changed regularly to keep the filter in good condition.

Reverse osmosis water filter membrane

This is the second stage in the water purification process of reverse osmosis water filter. The semi-permeable membrane will remove all impurities in the water that has passed through the pre-filter. The semi-permeable membrane is so fine that high pressure has to be applied for the purified water to pass through. The contaminants that was trapped will be flushed out as waste water.

Reverse osmosis water filter water tank

There is water holding tank to store purified water for consumption. The tank is needed to store a few gallons of purified water ready for consumption. The reverse osmosis process is slow and is not able to keep up with the demand. That’s why reverse osmosis water filter has to have a storage tank.