Is Reverse Osmosis Water Good for Coffee? Let’s Find Out!
Written by: Gene Fitzgerald // Last Updated: Jun 30, 2023
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If you are a coffee connoisseur, you may want to know if it is worth hooking up your reverse osmosis system to your at-home coffee machine.
Even more importantly, if you run a cafe and a good cup of coffee is vital for your income, should you use reverse osmosis water to get an edge over your competitors?
Let’s find out!
Contents
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Key Takeaways
- Reverse osmosis water has some advantages for brewing coffee but it does not have the specific composition of minerals and TDS required to brew the ‘perfect cup’.
- We would not recommend using reverse osmosis water for coffee brewing unless you remineralize it before.
Is Reverse Osmosis Water Good for Coffee?
So, is reverse osmosis water good for coffee? Yes and no.
Using reverse osmosis water for brewing coffee offers several advantages. Firstly, its high purity ensures no off-tastes interfere with the coffee’s natural flavors. Secondly, the absence of hardness minerals in RO water prevents scale buildup in your coffee maker, reducing the need for frequent maintenance and reducing the likelihood of parts degrading early.
However, there are some drawbacks to using RO water for coffee which we consider far more critical: The Special Coffee Association has defined the ideal type of water for brewing the perfect cup, which, among other things, states that the water should have around 100 ppm of TDS, particularly calcium, which RO water does not have. In other words, the lack of minerals in RO water will not extract the full flavor from your coffee beans. As such, coffee brewed with RO water often tastes rather flat. Additionally, the increased corrosiveness of the water can potentially damage metal components within your coffee maker.
Bottom line, we don’t recommend using reverse osmosis water for coffee brewing.
The Benefits of Using RO Water for Coffee Brewing
While RO water may not be ideal for brewing coffee, it does come with a few benefits.
Removes Chlorine
RO removes chlorine from the water, which can give coffee an off-flavor. It also removes other contaminants that can give water, and therefore your cup of coffee, a strange taste or smell.
Removes Harmful Contaminants
RO also removes contaminants like heavy metals, organic compounds, and bacteria. This helps to produce a cleaner and fresher cup of coffee and ensures it is safe for consumption.
Consistent Taste
As RO water has almost no TDS, it provides consistent coffee free from fluctuations should the taste and smell of your municipal water supply change.
No Scaling
And finally, with RO water you won’t have to worry about limescale deposits clogging your coffee maker.
The Cons of Using RO Water for Coffee Brewing
Removes Beneficial Minerals
The process of removing the harmful contaminants also removes the beneficial minerals like calcium, magnesium, and sodium from the water. This can lead to a flat or flavorless cup of coffee.
Increased Costs
RO systems can be expensive, so it may not be feasible for some people to invest in one just for the sake of making coffee. Plus, it adds to your water bill and costs for yearly maintenance.
Time-consuming
It takes a bit longer to brew coffee with RO water, especially if you have to wait for it to come out of the filter system or if your storage tank runs empty.
Corrosion
The last thing to consider when using reverse osmosis water for coffee brewing is its corrosive nature. RO water is slightly acidic and has a high affinity to dissolve substances. It will attack any metal component in your coffee maker it comes in contact with.
What If I Remineralize My Reverse Osmosis Water?
You may be able to get your RO water as close to perfect as you can by utilizing a remineralization filter. These filters raise pH and alkalinity and add calcium and overall TDS to the water. You would just have to ensure that the right minerals in the right amounts were being added.
Of course, you could also remineralize by hand!
Further Reading:
Coffee Science: Ideal Water Parameters (Chemistry)
The Specialty Coffee Association (SCA) has set guidelines for the perfect water for brewing coffee. As per the SCA, the water should have no smell, a transparent appearance, zero chlorine content, and a neutral pH level as close to 7 as possible. Hardness and alkalinity have also been defined:
- Odor: Clean/Fresh, Odor free
- Total Chlorine: 0 mg/L
- Calcium Hardness: 50-175 ppm
- Total Alkalinity: 40 ppm
- pH: 7.0 (Acceptable Range: 6-8)
Why TDS & Water Hardness Are Important
TDS and water hardness are important in the coffee brewing process as they affect the extraction rate and the coffee’s flavor. When water has a high TDS, it can cause over-extraction, which results in an overly bitter or sour cup. On the other hand, when water has too low a TDS content, it leads to under-extracted coffee with a lack of body and flavor. Similarly, water hardness also affects the extraction rate and can cause over-extraction if the water is too hard or under-extraction when it’s too soft.
Is Distilled Water the Perfect Water for Making Coffee?
Distilled water is not ideal for making coffee as it has the same issues as reverse osmosis water in that it has had minerals and TDS removed. This can cause the coffee to be under-extracted and lack flavor. The ideal water for making coffee is one with a balanced TDS content and hardness that allows for proper extraction.
What Else to Use?
- Some sources suggest using bottled water with a specific mineral content. This would be ideal for home coffee making, except it would not work for larger-scale applications such as cafes or restaurants.
- For larger coffee machines that you might find in a cafe, some may come with an in-tank filter. These filters reduce water hardness while preserving essential minerals for optimal flavor. Check with your coffee machine manufacturer for your potential options.
- Cartridge filters can be installed between your home plumbing and the coffee machine, which use ion-exchange technology to substitute scale-causing calcium with magnesium to maintain flavor.
If you have any questions about reverse osmosis water for coffee please don’t hesitate to leave a comment below!
About the Author Gene Fitzgerald
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