Reverse Osmosis is one of the most effective methods of water purification used today. This is because of its ability to filter contaminants of every type and ensure provision of high quality cooking and drinking water.

It features different types of filters in one system. It also uses a very effective filtration technology, the Osmotic Membrane. This is the part that takes care of minute organisms. They are left behind as pressure of 35-40 psi is applied to push water molecules through.

Different models of reverse osmosis systems are available in the market today. This can be accounted to the number of stages used in a system. Below is a description of the 3 stage and the 5 stage reverse osmosis systems.

Differences in Application

Though both systems are similar and are used for water purification, the applications are somehow varied. In most cases, 3 stage reverse osmosis systems are used for large scale purification of water. This can be by aquarium managers who want to protect their fish from harmful chemicals. They can also be used by farmers in saline environments to reduce the amount of salt contained in water for proper growth and maturation of seedlings.

5 Stage Reverse Osmosis systems on the other side are mostly used for provision of drinking and cooking water in homes. They only produce water that is not needed in high quantities.

Differences in Structure

As illustrated in their names, the 3 stage RO systems have 3 stages of filtration while the 5 Stage RO systems feature 5.

3 Stage RO Systems Structure

1.      The Carbon Pre- Filter/ Sediment Pre- Filter

The main purpose of this pre-filter is to remove sediment, in a bid to protect the RO membrane. In systems that use a carbon pre-filter, the carbon is also used for absorption of chemicals that bring bad taste and odour to water, e.g. chlorine.

2.      The RO Membrane

This membrane has tiny pores that only allow passage of water molecules, with the application of pressure. It filters all dissolved substances from the water.

3.      The post Filter

The main function of the post filter is to ‘polish’ the filtered water. It improves the quality of the water produced by removing any odour or taste that may have been left in the water.


5 Stage RO Systems Structure

1.      Polypropylene Sediment filter

The function of the polypropylene sediment filter is filter all solid substances from water, mostly sediment.

2.      Carbon Water filter

The carbon water filter is usually charged in most cases. It contains a negative charge which then attracts contaminants, since they mostly have positive charges. This makes them get eliminated from the water. The filter is also responsible for removing taste and odor from water

3.      1 Micron Polypropylene Water Filter

This filter clears up minute sediment particles (above 1 micron in size) that may have been left by the polypropylene sediment filter.

4.      Osmotic Membrane

This is the main filtration chamber in the system. It eliminates excessive minerals, metals like iron, lead, salts and nitrates among others.
Only water molecules can pass through the chamber. All other impurities, together with some water, are then piped out of the filtration system into the drainage system.

5.      Carbon Water Post-filter

Just like in the 3 stage RO system, the carbon water post-filter on this system removes all the remaining blemishes to make water ready for consumption


For these systems to function at their optimum level, they require proper care and maintenance. Regularly change filters to ensure you get high quality water. Contact us for more information.

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