4 stage vs 5 stage reverse osmosis: what is the difference

One of the common question beginners have for RO systems is the difference between 4 stage vs 5 stage reverse osmosis.  Today’s article will address in detail the purpose of the different stages in a reverse osmosis system and which type is ideal for your home purchase. Let’s get to it.

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6 stage reverse osmosis system reviewThe iSpring RCC7 is a 5th stage reverse osmosis system that is able to remove sentiments, unpleasant odor and taste as well as the undesirable chemicals in the water.

The system is able to reduce your water's TDS reading to around 10-14 ppm. It is also one of the more affordable RO 5 stage system in the market today.

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Purpose of multi stage reverse osmosis system

Currently, the market has different types of ro systems, ranging from one stage to 5 stage filtering.  Each type of filter generally has a specific role to perform. A pre setiment filter is usually the first layer of filtering that can remove many of the unwanted compounds like dust, particles, and rust.

To remove stuff like chlorine, carbon filters are usually added as the 2nd and/or third layer of filters. The reason for the 2 layers of carbon filters is that chlorine tend to impose strong stress on the filters so a two stage filtering shares the burden and improves the efficiency.

Finally, there might be a fourth stage membrane filtering to remove the finer unwanted chemicals like lead, fluoride, chromium etc.  This is what a 4 stage reverse osmosis system will usually do.


Difference between 4 and 5 stage reverse osmosis systems

Now we come to the 5 stage filter and the thing that differentiates between a 4 and 5 stage RO system.

For a fifth stage ro system, the last stage is usually remineraliation that I have talked about in my article on the best remineralization filter for reverse osmosis. The reason you need this is to add back the minerals that are good for your body. This is necessary because the 4th stage filtering usually removes them but we need them in our daily water consumption to have the right balance of minerals. An example of such a 5 stage reverse osmosis system is the Home Master that I have recommended as the best reverse osmosis system for 2015.

Some companies’ 5 stage filter is just a carbon based filter for improving the taste of the water.  This is the case of the Expresswater 5 stage reverse osmosis system that I have reviewed before as well as for the APEC ro system. So, you need to read carefully on what does the last stage filter do before committing to the purchase.


Which model is suitable for you?

From the above, you should one important criteria to decide between 4 and 5 stage RO system is remineralization. If you want it, which I suggest you do, then a 5 stage ro system will be more suitable.

In addition to remineralization, another criteria is the quality of your current water supply. If the water quality, as measured by TDM, is really bad, then having more stages in your filtering process is not a bad idea. Conversely, the water quality is not that bad, maybe even a 3 stage reverse osmosis system might be sufficient.

Finally, the water taste is another factor to consider. The last stage filter in some systems are purely meant for removing the odor and other stuff that affects the taste. If you want your water to taste crisp and pure then buying a 5 stage reverse osmosis system will make sense.



I hope this article has shed some light on the difference between a 4 and 5 stage reverse osmosis system. This understanding should help you to decide on which of these is a better fit for your home, bearing in mind your needs and criteria.

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