Does the kind of water you use really make a noticeable difference in the taste of coffee? Since a cup of coffee is made up of mostly water, the quality and type of water is hugely important. Water may seem simple with just 2 hydrogens and 1 oxygen, but it actually has more variety than first glance shows. Each water molecule has both a positive and a negative end. This polarity means that the negative oxygen on one water molecule is attracted to the positive hydrogens on the others forming hydrogen bond. However the motion of these molecules in liquid is dynamic enough to overcome the strength of hydrogen bonds and break them. These bonds are always being formed and broken; it's a natural tendency that has a number of effects in brewing. With hydrogen molecules breaking off and forming with nearby intact water molecules it leaves a negatively charged oxygen and hydrogen combination or OH and a positively charged H3O combination. This natural tendency to break and re-form is what is known as ‘dissociation” where 2-10 millionths of a percent of molecules are in this state. Seems like its barely enough to make a difference but it does and it's significant because even this tiny difference determines the acidity of the water.
The breakdown leaves behind hydrogen ions, whose basic units of positively charged protons can have a drastic effect on other molecules. A structure that has few protons around may be unstable when many of these protons are in the area. The arrangement of these protons are so important that we have a way of tasting these chemical compounds we perceive as sour or acidic. These chemical reactions can also be found in lemon juice, yogurt, milk egg whites, baking soda in water, orange juice, and coffee. We measure these protons by using a pH Scale which most people are likely familiar with. Neutral or “pure” water with a pH of 7 has an equal number of protons and OH ions. Anything below 7 has a greater amount of proton concentration so it tends to be more sour and anything above 7 has a lower amount of proton concentration, causing it to be more basic or alkaline.
Human gastric juice 1.3-3.0
Lemon Juice 2.1
Orange Juice 3.0
Black Coffee 5.0
Egg Whites 7.6-9.5
Baking Soda 8.4
Another huge factor that plays into water is mineral content. Originating from the ground that water is taken from, the mineral content can vary but the most common minerals that affect water hardness are calcium and magnesium. The higher the amount of these minerals the more it affects your coffee(or tea). These minerals can slow/block flavor extraction, cloud the brew, and reduce the espresso crema. In tea, it can cause surface scum from the calcium carbonate. Not to mention it clog up your espresso machine and leave scaly residue in your kettle.
So what can be done to solve mineral issues? Other than an expensive household water softener, the next best thing are refillable 18L water jugs. It's easy to choose and measure the mineral content at most water refill stations which makes it easy to get consistent tasting results. If you get your water from a municipality pipe the issues you will be facing will be different, usually being the off-flavours that come from disinfectants and water treatments. This issue can be solved by using a water filter but keep in mind these filters do not soften water so this will only do so much for hard water. Overall water varies from place to place and the solutions differ but either way water still plays a huge role in our cup. Try experimenting and comparing bottled, tap and distilled water in a blind test and let us know in an email what you think! Thank you for reading and I hope you have a great day.