Is Reverse Osmosis the Best Way to Filter Water?
Written by: Gene Fitzgerald // Last Updated: Oct 18, 2023
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Reverse osmosis is a superior water filtration process.
It can remove up to 99.99% of contaminants from the water, and with its added pre and post-filtration steps, the types of pollutants removed are vast.
But, is reverse osmosis the best way to filter water for you? It may or may not be. Let’s explore why.
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Key Takeaways
- Whether reverse osmosis is the best way to filter water depends on the type of water you’re starting with and what you want to achieve.
- To know what form of water filtration is best for you, test your water to determine what contaminants need removal.
- In many cases, reverse osmosis would be much more thorough than actually required. Where it comes in handy is when you are dealing with severe water contamination.
Is Reverse Osmosis the Best Way to Filter Water?
So, is reverse osmosis the best way to filter water?
Whether reverse osmosis is the best way to filter water largely depends on the type of water you’re starting with. For generally clean municipal water, RO is not the best choice. This is because drinking water contains essential minerals and salts that contribute to our health. RO removes many healthy minerals, which could lead to deficiencies like iron, calcium, manganese, and fluoride if your diet isn’t well-rounded. In such a case, reverse osmosis water treatment would simply be over the top.
However, in some cases, RO systems are the best choice. If you rely on a low-quality water source, RO is often your only option. If you rely on well water, for example, and live in an area with high concentrations of harmful contaminants (either naturally occurring or due to pollution), an RO system comes in very handy. For instance, RO is commonly used in farming areas with high nitrate levels in the groundwater due to extensive fertilizer use.
Reverse osmosis is also one of the few methods available to filter seawater and brackish water. That’s why you’ll often see onboard RO systems, or “water makers”, on ships or sailboats. Many countries, including the U.S., use large-scale RO systems to supplement or provide all their drinking water. These systems usually add minerals back into the water for taste and health reasons, but home RO systems may not unless you specify that you want a remineralization filter.
Home RO systems also have other drawbacks.
- They tend to waste a lot of water. This could be problematic if you live in an area with water restrictions.
- Plus, home RO systems operate at low pressure, so they produce water slowly and usually require a holding tank.
- And since this water doesn’t have residual chlorine from municipal treatment, it’s more susceptible to secondary contamination.
Have Your Water Tested
The key is not to simply purchase any water filter but rather to prioritize conducting water tests to identify the specific contaminants present in your water supply. This enables informed decision-making in selecting the most suitable filtration method to address any water-related concerns.
While reverse osmosis is highly effective, it might not always be necessary and, in some cases, could be considered excessive. Making informed choices based on water tests ensures you safeguard your water quality.
What Do You Want to Achieve?
If you aim to eliminate multiple or large amounts of harmful contamination from your water, a home reverse osmosis system is the optimal choice. However, if your primary concern is enhancing the taste and odor of your water, a simple carbon filter might do the trick. If you’re specifically looking to eliminate iron from your water, investing in an iron filter is recommended. In other words, there are various options available depending on your unique water treatment needs.
Further Reading:
What Is Reverse Osmosis, How Does It Work, and What Does It Remove?
Reverse osmosis is a water filtration process that utilizes an ultra-fine membrane to separate clean water from contaminated water. It’s used in various settings, including residential, commercial, and industrial applications and in desalination facilities.
The RO process applies pressure to force water through a membrane, which filters out contaminants larger than .0001 microns. This includes microbial contaminants, heavy metals, pesticides, herbicides, and various salts.
The concept of reverse osmosis is based on the natural phenomenon of osmosis. In nature, water from a less concentrated saline solution naturally migrates through a semipermeable membrane into a more concentrated saline solution until both solutions have equal concentrations. Reverse osmosis reverses this process using external pressure to push water from a high-concentration saline solution (the unfiltered water) through a membrane into a low-concentration saline solution (the filtered water).
Feed water enters the RO membrane chamber and is pushed through the membrane under high pressure. Contaminants larger than the membrane’s pores stay trapped on one side while clean water molecules pass through to the other side. The filtered water flows onward to the next filter stage, and the contaminant-filled wastewater is discarded. A well-functioning system should reject 95% to 99% of feed water salts.
The effectiveness of reverse osmosis in removing various dissolved ions is relatively high. For instance, it can remove 98% of aluminum and ammonium, 96% of arsenic, barium, cadmium, iron, lead, manganese, and 94% of chromium 6. It also effectively removes 97% of copper, mercury, nickel, phosphate, sulfate, sulfite, and zinc.
However, its efficacy varies for some other contaminants. It can remove 88% of chloride, cyanide, and fluoride and 90% of sodium. It is least effective at removing nitrates, with a removal rate of 68%. This is why most at-home systems have additional filters to ensure comprehensive water purification.
Pros and Cons of RO
Pros of Reverse Osmosis Water Purification
- Advanced Filtration: RO removes a wide range of organic and non-organic pollutants.
- Improved Taste and Aesthetics: By removing contaminants, sodium, and more, RO produces clean-tasting water and reduces turbidity, enhancing the water’s appearance.
- Health Benefits: The high purity of RO water can alleviate health concerns associated with contaminated drinking water.
- Cost-Effective: Compared to many other filtration methods or buying bottled water, using an RO system is less expensive, with minimal ongoing maintenance costs.
- Flexibility: RO filters are available in various sizes and configurations, allowing you to find one that fits your needs.
- Reduces Plastic Waste: Using an RO system at home significantly reduces reliance on plastic bottled water, reducing plastic waste and the risk of chemical leaching from plastic bottles.
Cons of Reverse Osmosis Water Purification
- Waste Water Production: RO systems produce wastewater as part of the filtration process, typically at a ratio of 4:1 waste to filtered water for home use. However, a pump can mitigate this, and wastewater can be repurposed for household chores.
- Mineral Loss: RO systems remove beneficial minerals such as magnesium, calcium, and potassium from water. However, water isn’t a significant source of these minerals in our diet, and you can always reintroduce these minerals post-filtration.
- Slow Filtration Speed: The RO process can be slow, requiring storage tanks for filtered water or powerful (and more expensive) pumps for faster filtration.
- Space Requirements: Home RO units require substantial space for installation.
- Potential Flat Taste: Some people find that RO water, stripped of most minerals and contaminants, tastes flat. However, many get used to this taste over time.
Is RO Water Safe or Is It Bad for You?
Reverse osmosis water is generally safe and beneficial, especially when it removes harmful contaminants from your water supply. While it’s true that RO filtration also removes healthy minerals, drinking contaminant-free water is likely safer.
Excessive consumption of RO water can accelerate mineral elimination from the body, mainly if you don’t obtain minerals from other sources. Although it would be ideal to retain beneficial minerals while filtering out harmful substances, this isn’t feasible with RO. Fortunately, lost nutrients can be replenished through remineralization before drinking.
Reverse Osmosis vs Other Water Filtration Methods
Let’s look at some of the filtration methods out there, aside from reverse osmosis, to help you make an informed decision regarding the right system.
Sediment Filtration
A sediment filter removes large particles such as sediment, silt, sand, and rust. They are often used as prefilters in a reverse osmosis system. On their own, they are mostly found as whole house water filters.
Carbon Filtration
Carbon filtration eliminates a wide range of contaminants, including chlorine, from water. It can help to create better-tasting and smelling water. It is often found in pitcher water filters and is always a key step in a reverse osmosis purification system.
Ion Exchange
Ion exchange filtration is a technique that swaps unwanted ions with preferable ones in an ion exchange resin. It relies on the interaction between a liquid, usually water, and a solid like resin or zeolite. This process is used in anion exchange, where a positively charged solid attracts negative ions, and cation exchange, commonly used in water softeners, where a negatively charged solid attracts positive ions.
Ion exchange is frequently used in water treatment to remove contaminants such as nitrate, arsenic, calcium, etc. It’s utilized in water softeners or water filters, depending on the end goal.
Ceramic Water Filtration
A ceramic water filter is a sediment filtration device with tiny pores dispersed across its surface, ranging from 0.5 to 50 microns. These pores trap suspended particles, preventing them from infiltrating the filtered water supply. While it may appear similar to reverse osmosis, the underlying process is not the same.
Many ceramic filters consist of a ceramic outer shell, with an inner core containing additional filtration media like activated carbon or ion exchange resin. This combination aids in the removal of contaminants that may have escaped the ceramic filter’s capture.
Ceramic water filters are not limited to gravity systems; they are also commonly employed in under-sink and countertop units.
Distillation
Distillation serves as an exceptionally efficient technique for purifying water. Utilizing heat to vaporize water and subsequently condensing the steam back into its liquid state eliminates a wide range of contaminants, just as well as reverse osmosis; however, it uses a lot more energy.
UV Disinfection
UV disinfection utilizes ultraviolet light to eliminate microorganisms and other impurities found in water. It is excellent for purifying drinking water from bacteria, viruses, and parasites, although it does not eliminate physical or chemical contaminants.
If you have any thoughts about the question, is reverse osmosis the best way to purify water, please don’t hesitate to leave a comment below!
About the Author Gene Fitzgerald
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