Making Coffee with Reverse Osmosis Water: Tasty or Awful

Making Coffee with Reverse Osmosis Water: Tasty or Awful

There are a lot of debates about the best way to make coffee. Some people swear by using reverse osmosis water, while others say that it makes the coffee taste terrible. So, what’s the truth? Is using RO water to make coffee a good idea, or should you stick to filtered or tap water?

Reverse osmosis can produce water that meets the primary requirements for making good coffee – no bad taste or odor and free of any chlorine. However, many baristas say that RO treated water makes a flat-tasting brew that lacks the complexity and body that makes a great cup of coffee. They point out that minerals like calcium and magnesium, which are removed by reverse osmosis, are what makes water and coffee taste good.

Making coffee is a little bit science and a little bit art. In this article, we’ll explore the pros and cons of brewing coffee with reverse osmosis water and help you decide whether or not it’s right for you.

Water and Brewing Coffee

Water is the largest constituent in a cup of coffee, and it plays an important role in the brewing process. Baristas know that clean, fresh water is important for making good coffee.

The water should be free of any off-tastes, odors or chlorine. However, even with these basic criteria, there is no guarantee of a great cup of coffee.

We do, however, have some helpful guidelines for brewing coffee:

  1. Having too many minerals in your water can negatively impact the quality of the coffee.
  2. If your water is too alkaline, it can give the coffee a soapy taste.
  3. Hard water can impart unpleasant tastes to the coffee, making it bitter or chalky.
  4. If the water has a low mineral content, it can cause undesirable extractions and tastes.

Reverse osmosis water for coffee

Reverse osmosis (RO) is a process where water is forced through a semipermeable membrane. Water passes through the small holes in the membrane, but dissolved solids and other impurities are left behind. This process can remove up to 99% of contaminants in the water.

Some people believe that using RO water to brew coffee produces a better tasting cup of coffee. The idea is that by removing impurities, you end up with a cup of coffee that tastes “cleaner” and less bitter. Using highly purified water from a reverse osmosis filter means the only flavors in your cup of joe are from the coffee.

Others say that RO water actually strips the coffee of its flavor. They argue that by removing certain minerals and compounds from the water, you end up with coffee that tastes flat and lifeless.

So, which is it? Does using RO water to brew coffee make a difference in the taste? Let’s take a closer look.

Read my other articles about reverse osmosis.
The Definitive Guide to Whole House Reverse Osmosis Filter Systems
Complete Guide to Under-sink Reverse Osmosis Filters

The science of brewing coffee

Brewing coffee is a very complicated chemical process known as “extraction”. In extraction, hot water is used to extract oils, caffeine, and flavor compounds from the coffee beans. The goal is to produce a solution that tastes pleasant and has the right balance of bitterness, sweetness, acidity and body.

The science behind extraction is complex, but we do know that minerals like calcium and magnesium play a role in what is extracted from the coffee beans. It also influences the amount of flavorsome compounds that are pulled out of the grounds.

The University of Bath conducted a study to determine the optimum concentration of cations (i.e., minerals) for making a great cup of coffee.

The researchers discovered that the composition of coffee can be controlled by adjusting the concentration of three minerals:

  1. sodium
  2. magnesium
  3. calcium

The report concluded by stating that if you want the best balance of flavors for a particular coffee, then either calcium or magnesium must be in the water. This suggests that using RO treated water may not be ideal because it removes all of these minerals.

The art of brewing coffee

Taste is a very subjective thing. What one person loves, another person may hate. When it comes to coffee, there are a lot of different factors that can affect the taste. The type of bean, the grind, the brewing method… even the water you use can make a difference.

Many people believe that using RO water to make coffee produces a tastier cup of coffee. The reasoning is that by removing impurities from the water, you’re also removing any potential flavors that could affect the taste. They argue that you want to taste the coffee, not the water.

Coffee roasters experiment with different beans, longer and shorter roasting times, and various temperatures to get the perfect bean. After roasting, they brew the coffee to see what it tastes like. The hardness of the water they use during this process is important because it contributes to the flavors and the final product. For this reason, when you make a cup of coffee at home, you should try to use water with similar hardness to what the coffee roaster used.

If you live in an area with hard water, then using RO water for brewing coffee may be a good idea. This is because the RO process will remove some of the hardness from the water, making it closer to the ideal brewing water.

Expert Opinions

Drinking coffee is a very personal experience. Some people like it dark and rich while others prefer it light and mild. Some people like it black while others add cream and sugar. The bottom line is that there is no right or wrong way to drink coffee. It’s all about what you like.

When it comes to brewing coffee, there are a lot of different methods and techniques. I find it’s always helpful to talk to the experts when I’m looking for advice. So, I reached out to a few coffee experts and asked them their thoughts on brewing with RO water.

1 – Barista opinions on reverse osmosis and coffee

I checked with several baristas and coffee shop owners about using reverse osmosis water to make coffee. They all had different opinions on the matter.

One barista told me that she always uses RO water to make coffee because it produces a cleaner tasting cup of coffee. She said that when she uses regular tap water, she can sometimes taste the chlorine in the coffee. But with RO water, she doesn’t have that problem.

The owner of a local coffee shop told me that he uses tap water filtered with activated carbon in his coffee shop because it’s the best way to ensure a consistent cup of coffee. He said that since water quality can vary so much from place to place, using unfiltered water can sometimes produce unpredictable results.

2 – What do coffee drinkers say about RO water

I’ve talked to a lot of coffee drinkers about this topic and there seems to be a split in opinion. Some people say they can taste a difference when RO water is used, and others say they can’t taste a difference.

Ultimately, the opinion that matters most is yours. If you like the coffee you make with RO water, then keep using it. But if you’re not happy with the results, try something else.

What is the Perfect Water for Making Coffee

Given the science and all of the various opinions on the subject, what is the perfect water for making coffee? Let’s explore this in more detail.

Specialty Coffee Association specifications

The Specialty Coffee Association (SCA) is a trade association that fosters global communities to help support activities in the coffee industry. This includes farmers, roasters and baristas across all parts of this value chain.

They developed a standard for the optimum water to make coffee with. In order to create a cup of coffee with exceptional quality, the water used for brewing should meet the following guidelines:

Characteristic Target Acceptable Range
Odor Clean Fresh / Odor Free Smells good
Chlorine None None
Hardness 50-175 ppm 50-175 ppm
Alkalinity 40 ppm At or near 40-70 ppm
pH 7 6-8

Water hardness is important

Water hardness is a measure of how much calcium and magnesium is present in water. These minerals enhance the flavor of water.

Think of these minerals like salt in cooking. A little bit can enhance the flavor of food, but too much can make it taste bad. The same is true for water hardness and coffee.

Water is a very good solvent. It dissolves most things, including the flavor components in coffee.

Water that has been treated with reverse osmosis is an even better solvent. As a result, RO treated water used to brew coffee may over-extract the flavors, resulting in very bitter flavors.

Pros and Cons of Reverse Osmosis and Coffee

Using reverse osmosis treated water to brew coffee has both benefits and drawbacks.

Benefits of using reverse osmosis water to make coffee

Reverse osmosis treated water offers the following advantages for making coffee:

  1. Eliminates scaling in coffee machine
  2. Removes chlorine and other bad tasting chemicals from water
  3. Removes contaminants like PFAS, arsenic, and lead from water

Disadvantages of reverse osmosis water to make coffee

Reverse osmosis treated water offers the following drawbacks for making coffee:

  1. Coffee tastes flat
  2. Extracts other flavor compounds from beans that many find objectionable
  3. Increases the bitterness of coffee
  4. “Aggressive” water can damage coffee machine

Using Reverse Osmosis Water to Make Coffee

As we’ve discussed, using reverse osmosis water to brew coffee is complicated. There are pros and cons to using RO water.

If you decide to use RO water, there are a few things you can do to improve the taste and quality of your coffee.

1 – Remineralize the water

Water with no minerals producing flat-tasting coffee. One way to address this is to add minerals back into the water. This can be done by using a water filter that has a remineralization cartridge.

The two most important minerals to add back are calcium and magnesium. The Bath study found that adding either magnesium or calcium alone improves the quality of coffee tremendously. Magnesium does not form scale, so this may be the better option.

2 – Match the coffee to your water

Not all coffee beans are the same. If you’re using RO water, try brewing with a lighter roast than you might normally use. The highly purified water tends to extract more out of the coffee than tap water does.

3 – Be consistent

Making a good cup of coffee requires attention to detail. Use the same amount of coffee and water each time. Small changes in any variable can result in a very different cup of coffee.

4 – Clean your equipment routinely

Make sure every piece of gear you use to make coffee is immaculate. Clean your grinder, coffee maker, and any other equipment you use on a regular basis. This will help ensure that your coffee tastes its best.

5 – Maintain your reverse osmosis system

Reverse osmosis systems need to be regularly maintained. The filters will eventually clog and need to be replaced. If you don’t maintain your system, it could start putting bad tasting water into your coffee.


Can you use reverse osmosis water in a Keurig?

If you’re looking for the perfect cup of coffee, don’t use mineral or spring water in your Keurig. They both contain high amounts of minerals which will ruin an otherwise great tasting brew! Distilled water and reverse osmosis treated water are a much better choice – they typically have less than 1 ppm of minerals.

Should I remineralize my RO water to make coffee?

Water that lacks minerals produces coffee that is flat and tastes diluted. Adding back minerals like calcium and magnesium can greatly improve the flavor and feel of your coffee. Many brands of reverse osmosis filters have optional remineralizers. These devices add minerals back into the water as it’s filtered.

What is the optimum TDS level for coffee?

The ideal TDS (total dissolved solids) for brewing coffee is between 50 and 175 ppm. Water with a TDS below 50 ppm will produce coffee that tastes weak and watered down. Water with a TDS above 150 ppm will produce coffee that tastes too strong and bitter.

I have a reverse osmosis system. Can I use the water to make coffee?

Reverse osmosis systems remove most of the minerals from water. This can leave your coffee tasting flat and diluted. If you want to use RO water for brewing, we recommend adding back minerals with a water filter that has a remineralization cartridge.

Final Take

So, should you be using reverse osmosis water to make your morning cup of coffee? The answer is a little complicated.

On the one hand, reverse osmosis does remove many unwanted compounds from your water and can help keep your coffee machine clean. On the other hand, this purer water can also strip away some of the flavors that make good coffee taste great.

Ultimately, it’s up to you whether or not you think reverse osmosis makes tasty coffee- just keep in mind the pros and cons we’ve outlined here. Do you have any experience brewing with reverse osmosis water? Let us know in the comments!


Boch Richard

Richard Boch is a chemical engineer responsible for designing water filtration systems for industrial and residential customers. He has more than 20 years of experience with ion exchange, activated carbon, and reverse osmosis. Richard's expertise has made him a go-to source for municipalities and businesses looking to improve their water quality. When he's not working, Richard enjoys spending time with his wife and two young children. You can also follow him on LinkedIn, Twitter and Facebook.

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