The Complete Guide to Understanding Water's Role in Coffee Making

15 min read JUN 24, 2024

Water plays a more critical role in coffee brewing than you might initially think. It's not merely one of many ingredients; it's the key to unlocking the full potential of your coffee beans.

Think of water as more than just a component; it's a vital solvent in coffee-making. Its role in extracting flavors from the coffee grounds is so significant that it deserves as much attention as your top-notch burr grinder or a beautifully crafted Japanese pour-over coffee maker.

My own revelation about the importance of water in coffee brewing came after a personal experience. Upon returning to Denmark from a lengthy stay abroad, I noticed a stark contrast in the quality of my coffee. The specialty coffee that tasted incredible when brewed with bottled water overseas lost its vibrancy and became dull when made with the regular tap water back home in Denmark.

This unexpected change was a wake-up call. I had, unknowingly, been enjoying coffee made with high-quality water, and the difference was clear. This realization set me on a years-long journey to delve deep into the world of water and its profound impact on coffee. It was a path filled with challenges and frustrations but led to invaluable insights.

In this post, I'll share those insights to spare you the same headaches and frustrations. You'll learn how the right water can elevate your coffee experience, transforming an ordinary cup into an extraordinary one. So, if you're ready to take your coffee brewing to the next level, keep reading and discover water's crucial role in the art of coffee making.

Role of Water in Crafting the Perfect Cup

The relationship between coffee and water is a well known concept among coffee enthusiasts. Considering that water makes up about 98.5% of a cup of coffee and about 90% of an espresso its impact on the final brew cannot be underestimated.

The topic of water in coffee brewing gained attention thanks to the collaboration between Maxwell Colonna Dashwood, a British barista champion and Christopher Hendon, an American chemist. Their groundbreaking work reached its pinnacle with the publication of "Water for Coffee" in 2015 marking a milestone in coffee research.

In their book Colonna Dashwood and Hendon extensively explore how different minerals and salts present in water affect the extraction process of coffee. They highlight magnesium and calcium as minerals that greatly enhance the extraction process bringing out the flavors in coffee.

However they also discovered that overall mineral content in water is not as crucial as previously believed. At least until a certain threshold is reached. What truly matters is finding the balance between hardness (which reflects levels of calcium and magnesium) and carbonate hardness (also known as alkalinity) which measures how well water can neutralize acids. Based on their research the ideal ratio for brewing coffee that is balanced and flavorful is a 2;1 ratio of hardness to alkalinity.

While getting a hold of 'Water for Coffee' may be difficult due to its limited availability, it is still a valuable resource for those with a strong understanding of chemistry and complex scientific concepts. For coffee enthusiasts looking to improve their brewing methods this book provides an insightful exploration of how water quality impacts the taste and overall quality of coffee. By grasping and applying these principles one can elevate a cup of coffee into an experience.

Role of TDS in Coffee Brewing

Before the enlightening insights shared in "Water for Coffee " Total Dissolved Solids (TDS) was widely regarded as a key measurement when evaluating water quality for brewing coffee. TDS encompasses all elements dissolved in water serving as an indicator of its purity and composition.

However Maxwell Colonna Dashwood and Christopher Hendon challenge this view, by advocating for a nuanced approach instead of solely focusing on TDS. Their argument is quite compelling when it comes to the importance of understanding how water hardness, buffering capacity and the specific minerals present, in water interact with each other.

From a coffee brewing perspective, the composition of water, including certain minerals like calcium and magnesium, plays a crucial role in extracting flavors from coffee beans. This means that relying on dissolved solids (TDS) measurements may not give us a complete understanding of whether water is suitable for brewing coffee.

Nevertheless, using a TDS meter remains a straightforward approach for coffee enthusiasts. Despite its limitations in providing information about water composition it still serves as a tool for those interested in experimenting with different coffee brewing techniques. It serves as a starting point for grasping the impact of water quality on the taste of coffee.

The Impact of Boiling on Water Quality

In his book "What I Know About Running Coffee Shops " Colin Harmon—an expert Irish barista and champion—shares advice regarding how boiling water affects the coffee brewing process. He highlights that boiling can deplete the oxygen content in water, which ultimately hampers its ability to brew effectively. According to Harmon, when water is boiled it loses its oxygen content resulting in a coffee, with a dull taste. To make sure that the water is in its optimal state for brewing he suggests using fresh water and stopping the kettle just before it reaches boiling point.

To demonstrate this at home Harmon proposes an experiment. Start by boiling a kettle of water, letting it cool down to room temperature, then boil it again and use it to make a cup of coffee or tea. After that discard the reboiled water and refill the kettle with fresh water. Boil it once. Prepare another cup of coffee or tea for comparison.

You should notice a difference between the two cups. The one made with boiled water tends to display vibrancy and has a superior flavor making it noticeably more enjoyable. On the other hand the brew made with reboiled water often tastes flat lacking in depth and complexity compared to using non reboiled water for brewing.

Water Options for Optimal Coffee Brewing

Navigating the complexities of water quality in relation to coffee brewing reveals a challenging reality: most tap water globally isn't ideal for making coffee. Even if it's safe and clean, the levels of calcium and bicarbonates often exceed what's desirable for brewing. Additionally, tap water may contain other compounds that negatively affect taste.

Given these challenges, there are several alternative strategies you might consider:

1. Filter Pitcher:

Like those offered by Brita and similar brands, a water filter pitcher can be a viable option if your tap water isn't excessively hard. For instance, if your tap water has a TDS below 200, using a filter pitcher can reduce it to a more coffee-friendly level.

An unconventional yet effective method is to filter your water twice. While it may seem rudimentary, this approach can significantly improve water quality.

However, a standard filter pitcher may be insufficient in areas with very hard water. It would be less effective, and the cost of frequently replacing cartridges could become prohibitive. In such cases, you might want to consider more specialized options.

An alternative worth exploring is the dedicated coffee filter jug from Peak Water. I've provided a detailed review of this product for your reference. While this jug presents a more tailored solution for coffee brewing, it also comes with its own set of limitations and is generally more expensive than regular pitchers.

2. Opting for Bottled Water:

Bottled water can be a practical choice for home baristas. In the United States, Volvic is a popular brand among coffee enthusiasts, while in the UK, Tesco's 'Ashbeck' is a preferred choice.

It's a good idea to experiment with various brands and let your taste buds be the judge. The more affordable options, typically labeled as "purified drinking water," are often better for coffee brewing. They usually have fewer minerals compared to pricier options.

High-end natural spring waters, such as San Pellegrino or Evian, are often laden with minerals, making them less ideal for coffee preparation.

3. Adopting a Pre-Made Mineral Formula:

Another increasingly popular method involves adding a mineral mix to Reverse Osmosis (RO) water. Third Wave Water is a renowned product in this category, designed to be added to a gallon of RO water. I find that using half a sachet is often sufficient to slightly reduce the intensity of the brew.

Other brands like Aquacode offer similar solutions, with their mineral mix purportedly sourced from deep-sea waters.

This approach is appealing due to its simplicity and consistency. This method is worth trying if you can easily find RO water or "purified drinking water" with a low TDS in your area. It offers a controlled and replicable way to ensure your water contributes positively to your coffee brewing experience.

4. Implementing Bypass Water:

A technique commonly used in coffee shops is the "bypass water" method. This involves starting with a primary water source devoid of minerals, typically Reverse Osmosis (RO) water. Then, a small amount of tap water is added back to introduce a slight degree of hardness and alkalinity, aiming for a more balanced and natural taste. The amount of tap water needed depends on its hardness; a 10% mix might suffice in areas with hard water.

An example of this practice is The Coffee Collective in Denmark, which targets a TDS level of about 30, indicating extremely soft water. This precise balancing act results in water that's ideally suited for coffee brewing.

5. Crafting Custom Water Recipes:

Many home baristas are now experimenting with creating their own mineral blends for coffee water. The foundation for these experiments is a source of ultra-pure water, ideally with a TDS between 1 and 10.

While reverse osmosis water is readily available in some regions, it can be more challenging to find in places like Scandinavia.

Common ingredients for these DIY mineral blends include Epsom salt (providing magnesium) and baking soda (supplying bicarbonate), which are easily found in supermarkets or health food stores. Some recipes also incorporate calcium, known for enhancing the mouthfeel and offering a more 'natural' taste compared to magnesium.

The initial investment in these minerals is modest, typically around $15, but it allows you to produce hundreds of gallons of customized brewing water. This approach offers a cost-effective way to tailor your brewing water to your taste preferences and enhance your coffee experience.

Creating Custom Mineral Concentrates for Coffee Brewing

Tailoring your water for espresso and filter coffee can significantly enhance the flavor and quality of your brew. Here are some recommended recipes for creating mineral concentrates:

Espresso Water Concentrate:

For espresso, try the "rpavlis" basic recipe. Start by dissolving 1g of potassium bicarbonate in 100 ml of RO (Reverse Osmosis) water to create your concentrate. Add 10g of this concentrate to every liter of water when brewing. For darker roast coffees, reduce the concentrate amount to 5g per liter to achieve a balanced profile.

Filter Coffee Concentrate:

For filter coffee, a two-part formula without magnesium is currently my preference.

Calcium Concentrate: Dissolve 5g of calcium chloride dihydrate in 500ml of water. This solution is your calcium concentrate. Adding 10g of this concentrate to 1 liter of water results in a calcium content of 67 ppm (parts per million).

Alkalinity Concentrate: Mix 1.5g of baking soda and 1.5g of potassium bicarbonate in a separate container with 500ml of water. This is your alkalinity concentrate. Using 10g of this solution per liter of water provides an alkalinity of 33 ppm.

When preparing your brew water, add the calcium concentrate first, followed by the bicarbonate mixture. This sequence ensures proper mineral integration.

You can adjust the mineral content according to your preferences. For instance, using only 5g of each concentrate per liter of water will halve the mineral content, resulting in 33.5 ppm of calcium and 16.5 ppm of alkalinity. These tailored mineral concentrates allow you to fine-tune your water to suit different types of coffee and personal taste preferences, giving you control over every aspect of your brewing process.

Redefining Priorities: A New Perspective on Coffee Water

Since my initial exploration into the world of coffee water, my understanding and preferences have evolved. While the above information provides valuable context, I'd like to share my updated views reflecting my current stance on this topic.

Emphasizing Flavor Over Theory

The early discussions around coffee water heavily focused on the scientific insights from the book "Water for Coffee" and various blog posts from Barista Hustle. This book introduced several key concepts, such as the ideal hardness-to-alkalinity ratio of 2:1 and the importance of magnesium and calcium in coffee extraction.

Barista Hustle expanded on these ideas, creating water recipes that primarily utilized baking soda and Epsom salt. However, after extensive experimentation, I've realized that these formulations don't always align with my taste preferences. I've found that water with a high concentration of magnesium often imparts an artificial flavor to the coffee. Even when balanced with calcium, I prefer only a minimal presence of magnesium.

Moreover, I've discovered that water recipes with high TDS levels can be too intense for my liking. I now gravitate towards water with a lower TDS, typically in the 40-80 range. There are exceptions, especially with certain light Scandinavian roasts, where a higher hardness level can enhance flavor extraction.

Interestingly, many renowned coffee shops and roasters are moving away from the strict magnesium and 2:1 paradigm. They're opting for softer water with a more natural composition, often achieved by mixing RO water with tap water to reach a desired TDS, usually between 30-60.

A study by Royal Coffee, a leading coffee importer, further supports this shift. Their professional cupping team conducted blind tastings with various minerals and water formulations, concluding that calcium is generally preferred over magnesium, and distilled water often outperforms specialized formulations like Global Customized and Third Wave Water.

The Importance of Consistency

My second principle is that consistency in water quality is more crucial than occasional perfection. Even minor miscalculations can significantly impact the brew when you start experimenting with different mineral compositions. From my experience, such experiments can easily overshadow the focus on the coffee itself.

A consistent water quality allows for more control over other brewing variables. The aim is to make water a constant factor, thereby simplifying the brewing process and enhancing your focus on the coffee.

Finding Practical Solutions

The third principle highlights the importance of convenience. You don't necessarily need perfection; the goal is to avoid water that masks the flavors of coffee. This can be quite challenging since many types of tap water are not suitable for brewing coffee.

The ideal solution varies depending on where you're. In some areas you may have access to water, which works well for brewing coffee. In regions using a water filter pitcher could be enough to improve and soften tap water. Alternatively using water with a specific amount of mineral concentrate like Third Wave Water can also be effective.

The key is finding a water solution that's easy to handle and consistent. Simplifying this aspect of your coffee routine can enhance your brewing experience. Make it more enjoyable.


My perspective on coffee water revolves around a simple yet powerful concept; it should be "good enough." Striving for perfection like achieving a 2;1 hardness to alkalinity ratio can often become unnecessarily complex.

In many situations using water with a TDS (Total Dissolved Solids) ranging from 30-100 is more than adequate to make your coffee exceptionally good. Why? The TDS range of this water ensures that its alkalinity is naturally low so it won't have an impact on the coffee's acidity.

While some experts argue that TDS alone isn't sufficient to determine water quality they make a point. In theory the dissolved solids could be anything from table salt to compounds. However they typically consist of a balanced combination of salts and minerals.

Thus the suitability of water for coffee can vary. Some coffees may taste best when brewed with water at the lower end of the TDS spectrum, around 30, while others might benefit from water closer to 100 TDS.

Although experimenting with custom mineral compositions for water can be fascinating I've come to believe that it doesn't necessarily result in a coffee experience. Instead of striving for perfection, focusing on achieving "good water quality often leads to an enjoyable and less complicated coffee brewing process.

Frequently Asked Questions (FAQs)

1. The Suitability of Tap Water for Coffee Brewing

Many home brewers commonly use tap water for making coffee. Whether this is safe or not largely depends on the quality of your water supply. In most cases tap water is generally safe to consume. However when it comes to enhancing the taste of your coffee tap water may not always be the best option, due to its varying mineral content and potential impurities.

2. The Use of Spring Water in Coffee Making

Using spring water for brewing coffee can be an option. It's important to consider its mineral content. Surprisingly many popular brands of spring water have a mineral content that may not be ideal for achieving the flavor extraction in your coffee. In some cases more affordable alternatives labeled as 'purified water' could be a choice as they usually have a lower and more suitable mineral content for brewing a well balanced cup of coffee.

3. The Effectiveness of Alkaline Water in Coffee Preparation

There is some debate surrounding the use of alkaline water for making coffee. While it is certainly preferable to avoid extremely alkaline water the ideal scenario would involve using water with a neutral pH close to 7. This pH level ensures that the water does not interfere with the flavors and acidity of the coffee resulting in an authentic and enjoyable coffee experience.

4. Can Distilled Water Be Used for Coffee Brewing?

Technically distilled water is safe for coffee brewing but it may not be the best choice. The process of distillation removes not only impurities but also essential minerals that contribute to the taste and extraction of coffee. Using distilled water can result in a lackluster flavor in your coffee. However if you have no option but to use distilled water you can enhance its suitability for brewing coffee by adding a mineral concentrate like Third Wave Water. This will reintroduce the minerals for flavor.

5. How Does Hard Water Affect Coffee Brewing?

The presence of water which contains levels of minerals such as calcium and magnesium can significantly impact the taste of your coffee. While these minerals are necessary for excessive extraction an excess amount can lead to over extraction resulting in an imbalanced cup of coffee. Additionally hard water can cause scaling in your coffee equipment potentially reducing its lifespan and efficiency. If your tap water is considered hard, using a water filter pitcher or mixing it with distilled water can help achieve a balance when brewing your coffee.

Check out Lifeboost Coffee Gifts & Coffee Accessories.

Drop a Comment

All comments are moderated before being published


This article is incredibly insightful! I never realized how crucial water quality is in coffee making. The detailed breakdown of minerals and their impact on flavor was particularly enlightening. Thanks for providing such a comprehensive guide—it’s definitely going to improve my morning coffee routine!