If you’re confident in your domestic brewing abilities and have a state-of-the-art coffee maker, it can be frustrating if the coffee you produce is inferior to what you’d expect in a coffee shop. One regularly overlooked potential issue is the type of water you’re using.
However, it’s a crucial consideration because a cup of coffee is around 98% water. But what is the best water for coffee and how do you determine whether your water source is acceptable?
Let’s look at those questions, and discover your options for achieving the best water for coffee.
What Kind Of Water Is Best For Coffee?
According to the Specialty Coffee Association, the best water for coffee should contain 68mg per liter of calcium with an acceptable range between 17mg per liter and 85mg per liter. It should also have 40mg per liter of alkalinity, and a pH of 7 (although a range between 6.5 and 7.5 is acceptable). [1]
The best water for coffee has the ideal balance of mineral ions – namely calcium and magnesium. We also need to ensure we have the correct level of buffer or alkalinity. Calcium and magnesium are useful for extracting coffee flavor compounds. Without them, there would be very little extraction.
Meanwhile, alkalinity balances the acidity. Too little and you will have an unpleasant and sour beverage. Too much, and the coffee will be dull and largely tasteless.
There are other factors to consider too, including the odor and color of water. Meanwhile, there are several approaches you can take to check exactly how much of each your water contains, but the easiest is probably to look it up online. Many water authorities will give you a detailed summary of the water in your area. [2]
Water Factors That Affect Brew Quality
Several key factors of the water affect the brew quality. Let’s go over what each of those are, what they mean and their effects.
Water Hardness
Water hardness is determined by the amount of dissolved minerals in water – largely calcium and magnesium [3]. The concentration of those two minerals determines the extraction of the coffee flavors. It’s worth noting, too, that too much calcium and magnesium causes scale to build up in your coffee maker so more is not necessarily better.
According to a study by Seven Miles and University of New South Wales, the optimum concentration of calcium and magnesium in water for the best possible extraction is between 50-80 ppm [4]. If the concentration falls below that number, your coffee extraction is likely to be weak and insipid. Not surprisingly, the more calcium and magnesium there is, the higher the extraction will be. However, once the number reaches above 80 ppm, there are diminishing returns.
This is useful, because it means we have a clear window to aim for. Also, it’s good to avoid the concentration going over 80 ppm because that will create more scale, which will damage your equipment in the long run. Certainly, if it reaches above 95 ppm, that is an increasing concern. Some coffee makers come with water hardness test strips so that you can test your tap water.
Another consideration is filter coffee, which is more sensitive to water composition because it is more diluted than espresso. Generally, soft water is better with filter coffee.
pH Level
The pH level refers to the acidity of the water. The magic number in this case is 7, and that’s what the SCA recommends too.
A pH level below 7 makes the water more acidic, while a pH level above 7 makes it more alkaline. In reality, there is some leeway – an acceptable range is between 6.5 and 7.5.
Coffee is naturally acidic with low pH, so if you brew coffee with acidic water, the coffee taste will be sour and unpleasant.
As with the hardness, though, there is a ceiling – anything above 8 and there will be more gas when the coffee grounds touch hot water, which can affect the flow of the coffee.
Overall, water that is ideal for coffee brewing needs a balance of mineral ions and alkalinity.
TDS (Total Dissolved Solids)
TDS refers to the total dissolved solids in the tap water. These solids are naturally occurring. When rain falls, it dissolves the minerals of the rocks and soils it stands on. As the process continues, the minerals remain in the water at various concentration levels. That’s why some areas have harder water (more dissolved minerals) and some areas have softer water (fewer dissolved minerals).
The SCA recommends an acceptable range of TDS is between 75 mg/L and 200 mg/L. One way to measure your tap water is to use a TDS meter [5]. That will tell you the total amount of dissolved solids in your water to offer a useful guide when determining the quality of your water for brewing coffee. However, there is a caveat – they don’t give information on what the solids are.
Water Temperature
Finally, we need to consider the water temperature, which should be between 195F and 205F (90C and 96C).
If the water temperature is too high, volatile compounds are released to quickly making it hard to control the extraction process. That means you are more likely to get a more bitter or sour-tasting coffee. On the other hand, water that is too cool will not extract enough of the desirable flavors leading to a weak and under-extracted coffee.
How To Improve Water For Coffee Brewing
If You Use Tap Water For Coffee
The first thing to note is that while tap water is the most convenient and accessible option for brewing coffee, it won’t offer the best results.
However, if you do use tap water, a good idea is to use a water filter pitcher. They work by using a filter mesh to remove matter. The filter also contains lots of tiny beads.
There are two types of beads in each filter: one is active carbon (essentially charcoal) which helps remove unwanted tastes including chlorine. The others are ion exchange beads that absorb the calcium and release a sodium ion in its place.
A water filter pitcher certainly helps soften water, but it won’t make it perfect and is mainly concerned with removing unwanted flavors.
If your water is very hard, one option is a reverse osmosis (RO) filtration system which pressurizes water against a mesh that is so fine only water can get through. i.e. not the minerals.
There are some issues with this process. As well as being wasteful, it results in almost entirely purified water, which isn’t ideal as it lacks the mineral content needed for the best coffee.
However, there is an effective way to counter this issue: you can add a premade formula with the perfect ratio of minerals to your RO water (or distilled water). Third Wave Water is one brand that provides the formula.
Try Using Bottled Spring Water
One of the most quick and accurate solutions is to use bottled water. If you check the label, it should have the mineral content on it, so you can see straightaway if the water contains the right parameters for brewing coffee.
One downside of bottled water is, of course, the plastic waste. However, it is probably the easiest way to ensure your water is perfect for brewing coffee.
Making Your Own Coffee Water Recipes
Lastly, you can attempt your own water recipes. To do this, you will need baking soda, Epsom salts, deionized water and a scale.
A useful resource for determining the precise levels you’ll need is Barista Hustle [6], which lists several recipes and also has a water calculator app where you can input specific levels to create the ideal recipe for the particular water you have.
FAQ
While there are many questions on the best water for coffee – and how to achieve it – there are some particularly common questions. Let’s try to answer them.
Filtered soft tap water or bottled water are the best options for brewing espresso. If you use distilled water or RO, they are such effective solvents that they can – over time – begin to leach minerals out of the metal pipes of your machine, causing corrosion.
Starbucks employs a Triple-Filtered Reverse Osmosis water filtration system. As the name suggests, there are three stages of filtration. Water flows through filters to remove various sediments, before it then reaches an active carbon filter, where unwanted flavors such as chlorine are extinguished. Then, it goes through a membrane made from a thin film composite material to remove smaller impurities.
It’s not recommended to use distilled and purified water for brewing coffee, because the minerals needed for the ideal extraction will not be present. This can lead to a mediocre and quite bitter cup of coffee.
Final Thoughts
It can be easy to overlook the importance of your water type for brewing coffee. However, if you are confident that your brewing methods, machinery and bean quality are ideal, but your beverage isn’t as good as you’d like it to be, it could be time to examine the water quality.
While the subject may seem complex, it can be broken down into four main areas – hardness, pH level, TDS and temperature. As to how to ensure you have the optimum levels of each, there are several options to consider.
Hopefully, once you have arrived at the best solution for you, it will only be a matter of time until your coffee reaches a level of quality you could expect in a coffee shop.
References:
[1] Water for Brewing Standards – http://www.scaa.org/?d=water-standards&page=resources
[2] WATER HARDNESS MAP – https://www.hydroflow-usa.com/water-hardness-map
[3] Hardness of Waterhttps://www.usgs.gov/special-topics/water-science-school/science/hardness-water
[4] The Science of Perfect Water for Coffee – https://www.sevenmiles.com.au/blogs/editorial/the-science-of-perfect-water-for-coffee/
[5] What is a TDS meter and do you need one? – https://www.aquasana.com/info/tds-meter-what-is-it-and-do-you-need-it-pd.html
[6] DIY Water Recipes Redux – https://www.baristahustle.com/blog/diy-water-recipes-redux/
