5-Stage vs 7-Stage Reverse Osmosis Systems
Written by: Gene Fitzgerald // Last Updated: Aug 14, 2023
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7-stages in a reverse osmosis system might seem excessive, but if you are looking at a 5-stage, you might figure a couple of extra add-ons will give you the best quality water.
But will they? Or are you wasting your time, cabinet space, and money?
Let’s look at a 5-stage reverse osmosis system compared to a 7-stage one so you can decide what you need.
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Key Takeaways
- 5-stage and 7-stage reverse osmosis systems will all have sediment and carbon pre-filters, a reverse osmosis membrane, and usually a post-carbon filter. Where they differ is the number of more “special” filter stages like UV purification and remineralization.
- 7-stage RO systems are more likely to have more of these “special” filter stages.
- Which setup is ideal for you depends on your water quality and preferences.
5 vs 7-Stage Reverse Osmosis Systems – Differences
5-stage and 7-stage RO systems will all have a sediment pre-filter, a carbon pre-filter, a reverse osmosis membrane and usually a post-carbon filter. These filters can be in different configurations. For example, there may be two sediment pre-filters and one carbon pre-filter. Or two carbon pre-filters and one sediment pre-filter. It depends on what is in your water.
5-Stage Reverse Osmosis Systems
- The sediment pre-filter(s) effectively removes dirt, sand, and other debris like rust.
- The carbon pre-filter(s) works to minimize bad tastes and smells in water by reducing elements such as chlorine.
- A reverse osmosis membrane eliminates most of the contaminants in the water, up to 99%!
- The polishing filter, another activated carbon filter, ensures that the water is top-quality before being dispensed from your RO faucet.
- In addition, there might be a UV light stage for elimination germs or a remineralization filter for adding calcium, magnesium, and other minerals back into the purified water.
7-Stage Reverse Osmosis Systems
A 7-stage reverse osmosis system includes all the features of the 5-stage system but most likely adds two “special” filters: UV + remineralization. So:
- Three pre-filters (sediment + carbon)
- The RO membrane
- A carbon post-filter
- A remineralizer
- And UV
The Different Filter Stages in a Reverse Osmosis System
Let’s look at each stage individually to see which ones you might need and which may be overkill.
Sediment Filters
Sediment filters eliminate debris. Positioned at the start of the filtration process, it captures larger particles, enhancing the efficiency of subsequent steps in filtration. Consider it as assisting the rest of the system in filtering smaller substances more effectively.
Carbon Filters
During the carbon filtration stage, water passes through the carbon, eliminating chlorine, chloramines, and possibly even pesticides, VOCs, disinfection byproducts, and lead among other stuff.
Removing chlorine is of special interest here (chlorine can damage a reverse osmosis membrane).
Reverse Osmosis Membrane
During this critical stage, water passes through a semipermeable membrane encompassing pores as minuscule as 0.0001 microns. An astounding 99% of impurities, both dangerous and not dangerous, are eliminated from the water. This step is not an ‘optional’ one in any reverse osmosis system.
UV
Adding a UV purifier to an RO system is beneficial when the feed water contains microorganisms such as bacteria, cyst, or viruses. This purification stage utilizes ultraviolet light to scramble the DNA of pathogens in the water and prevent their proliferation.
Remineralization
A remineralization filter is an additional filtration stage that restores the water’s natural minerals, such as calcium and magnesium. RO removes these ‘good’ minerals as well as all the ‘bad’ things. This helps improve the taste of the water while increasing its pH level, which some individuals favor.
5-Stage vs 7-Stage Reverse Osmosis Systems – Which One Should You Choose?
So, 5-stage vs 7-stage reverse osmosis system – which one should you choose?
It depends on your water conditions! If your water does not have microorganisms, then a UV filter is not a necessary add-on. And a 5-stage RO system can already include remineralization, so it could be perfectly fine. However, if you require both UV and remineralization, and possibly even another “special” type of pre or post-filter, 7-stage may be the way to go!
Is More Filter Stages Always Better?
More filtration stages only mean better when it is what your water needs. Water from different sources has different compositions, and sometimes even more than 3-stages of filtration would be overkill (especially if your source water is municipal water).
Manufacturers frequently enhance the filter stages in their systems for marketing and upselling. Nevertheless, the performance of a filtration system is not solely dependent on the number of steps. To achieve higher rates of contaminant removal, finding a balance between using different types of media or methods and increasing the volume of the same media is key when it comes to filter stages.
Your Water Quality
To determine your particular requirements, it is advisable to test your water and identify the substances you wish to eliminate. This is especially true if you have private well water instead of municipal water, which is more tightly regulated.
What Do You Want?
When selecting the stages of your RO system, personal preference is a deciding factor. If you simply don’t want your municipal water to taste like chlorine anymore, then a carbon filter might be enough. However, if you seek guaranteed pure water, opt for a reverse osmosis system.
How Much Are You Willing to Invest?
Typically, the system’s cost increases with the number of filtration steps. This applies not only to the initial purchase but also when factoring in the expenses associated with filter replacements in the annual running costs.
Installation
As the system size and number of stages increase, installation becomes more challenging. A self-installation at home is relatively easy for a 3-stage system. However, a 10-stage system can be quite complex, especially if space is limited.
Maintenance
The maintenance required for an RO system is generally determined by the number of filtration steps involved (more steps means more care).
If you have any questions about 5 vs 7-stage reverse osmosis please don’t hesitate to leave a comment below!
About the Author Gene Fitzgerald
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