While we spend a lot of time and effort searching out specific coffee blends, roast profiles and the best machines to turn it into liquid gold, most of us forget that water makes up most of what we are drinking. Too little thought goes into what is in the water and how those chemicals can affect the taste of our brew. The chemical composition of that water can also affect the temperature of your coffee and even worse is that the water you pump through your coffee machine, can impact its lifespan.
So how does water composition impact your cup of coffee?
First, different chemicals in your water can not only alter the taste of your coffee but may also be harmful to human health (see this article on PFAS chemicals and how Microfilter has become the first NFAS/ANSI 53 accredited company with water filters to reduce these harmful compounds).
Water contains many dissolved chemicals such as calcium, sodium, magnesium and hydrogen carbonate (which greatly impacts the alkalinity of the water). Then most of us will use municipal water in making our coffee and there we find chlorine which is added to water to reduce the risk of illness. Hydrogen carbonate plays a key role in defining coffee flavour because it reacts with the caffeic acids that bring coffee alive, and that results in greater bitterness and a loss of the more perky flavours. We talk more about this in our article on why you need a water filter for your coffee machine.
So the concentration of these components in the water will determine the hardness of the water and affect coffee taste profiles. That is why coffee can taste so different in Cape Town to a Johannesburg resident!
Second, the presence of calcium in water can lead to scale build up on the metallic parts of your coffee machine. Calcium deposits, called calcium scale, are really effective insulators and hinder the transfer of heat from boiler to water. This becomes particularly noticeable in what are called thermoblocks or “flash” boilers that are found in small automatic coffee machines. These are blocks of metal that have channels through which water flows, and as it does, it is heated by the contact with the hot walls of the many channels.
That is, until a calcium layer builds up on the surfaces of the metal and keeps the water away from the metal surfaces. You’ve probably seen this in your domestic kettle and it is a real issue for coffee making because the temperature of the water is a critical factor in extracting desirable coffee compounds and leaving behind the less desirable compounds.
If you’re a little sceptical, you can easily taste the difference by simply pouring 500ml of 50 C water through 50g of ground coffee and comparing the taste to the same quantities, but at 80 C. Water temperature is important!
Third, scale build up can result in water blockages and place undue pressure back on the pump, which can wear or fail, never mind deliver less water through your coffee.
From the discussion above, removing calcium from water helps to reduce the build-up of limescale but removing it all will also result in a poor tasting coffee. The Specialty Coffee Association (SCA) of America has set the ideal calcium level in brewing water as being between 17 and 85mg/l and so filters must remove all but this amount if they are to be used. In addition, the SCA has determined that total alkalinity should be at 40mg/l; pH between 6.5 to 7.5 and sodium at 10mg/l. Finally, there should be no chlorine and the total dissolved solids should be between 75 and 250mg/l.
Filters like the FX-10 water filter are designed to do just this.
Which filter should you use with your coffee machine?
Filters need to chosen according to the quality of the water in your area. If you live in an area with soft water, you may not need a filter that removes calcium and also just remember that if your water is extremely soft, you may have to add minerals because soft water with its lower pH and total dissolved solids, can be very corrosive.
A rapid test can determine this in minutes and a filter that is fit for purpose can be installed.
Where we need to only remove chlorine, dirt and bacteria, we use what is known as a “carbon block” filter and where we have excessive calcium and magnesium in the water, we prefer to use an “ion exchange resin” filter rather than systems such as reverse osmosis that removes all minerals. The reason being that these filters do not allow the water to become mineral depleted or acidic as they remove calcium while replacing it with another cation such as sodium.