It is easy to forget that coffee is mostly made up of water, and it is the biggest ingredient by weight. In an espresso alone, around 85% of the drink is water, and that is considerably more in taller coffees.
But how many of you out there just fill the kettle straight out of the tap, or use unfiltered water in your machine? With over 60% of the country having hard or very hard water, this could cause problems for all sorts of reasons, from changing the taste of your coffee to damaging the internal workings of your machine.
However, minerals aren’t always a really bad thing…
What Is Hard Water?
Hard water contains a lot more mineral content deposits than filtered, or soft, water. They are formed when water is naturally flowing through deposits of limestone, chalk, or gypsum.
Whether your water is naturally hard or soft straight out of the tap all depends on geography, unfortunately. In areas mostly made up of non-porous surfaces such as granite, the water simply runs off surfaces rather than permeating them, meaning it is softer.
Scotland, Northern Ireland, most of the North of England, and the South West have soft water, while a lot of the Midlands and West of England have hard water. Bad news if you are in the East and South East though – your water is likely to be very hard. You will probably realize the difference when washing dishes, washing your hair or even just the general taste, look, and feel of the water.
How Does Water Quality Affect The Taste Of My Coffee?
According to research, water hardness levels can make or break a cup of coffee. If you read below, you will actually see that not all mineral deposits are bad for the taste and extraction method, but they should generally be kept at small doses, which can make the issue of filtering more difficult.
But one argument for filtering the water is that it means a more consistent taste. Water hardness can actually change ever so slightly from day to day, depending on how much it has rained for instance, so that also means that no two cups of coffee may ever taste the same. Thus, water can drastically affect how well you can taste the different flavors your coffee naturally inherits.
Are All Water Minerals Bad For Coffee?
Actually, no. These are some of the most common minerals found in water in the UK, and the effect they will have on your hot beverage:
- Carbonates – Calcium carbonate can form on equipment, especially if the water also contains a lot of calcium. But a touch of carbonate could be good as it cancels out any acid present.
- Calcium – The mineral behind most limescale problems, and also one of the most commonly found. But a touch of calcium can help with extraction, so you don’t want to remove it all.
- Magnesium – Less common than calcium, but can also help with extraction so some present in your water isn’t all bad.
- Chlorides – There are two types of this, sodium and potassium. Sodium chloride is salt, which is not a good idea in coffee, and there are studies to suggest it can swell coffee too, reducing extraction efficiency. It’s usually best to filter chlorides.
- Iron & Copper – Usually enters the water supply via older pipes. This causes a metallic taste, so should be filtered out.
- pH – Not a mineral as such, but acidity and alkaline levels can affect taste too. The scale goes from 1-14, with 7 being completely neutral, and between 6.5 and 7.5 is acceptable.
How Can Hard Water Affect My Coffee Machine?
Mineral deposits can start to build up in your coffee machine a lot quicker than you’d imagine. Some of the compounds are ‘sticky’, so will attach themselves to any surface they pass through, especially if this is metallic.
Think about the way your coffee machine works and how the water ends up in your cup; you fill a tank, the water is heated, it travels through the machine to be passed over the grounds and is then dispensed through the water head.
Even with manual forms of coffee preparation, the water touches a lot of parts of the unit and travels through tubes, through filters and pourers.
If you have a warranty or guarantee on your coffee machine, then there is even worse news if you don’t keep on top of filtering. Any problems caused by mineral build up are often not covered, as part of the warranty will involve regular maintenance and cleaning. This includes descaling. You have been warned…
How Do I Get The Ideal Water Composition?
Confusing, isn’t it?
Hard water is generally bad (especially for your machine), but soft water will mean a harder job extracting the flavors. Some minerals are really bad for coffee, but some are fine in small doses. So how do you make your water exactly right for coffee?
The simple answer is that not all water filters are the same. There are many available, including ones that take away all of the undesirable additions listed above while leaving small traces of calcium and magnesium. Activated carbon/charcoal options can be good, as they fully clean the water before putting minerals back in.
Test your water beforehand to see what is present, as there may not be anything there which can have a negative effect. If you live in a very hard water area though, it is probably worth it.
Filtering can be better than buying bottled water, as not only are you not using all that plastic, but bottled water may not contain the minerals required. It is used to drink and not just make coffee with, after all. Depending on the results of your test, you can:
- Stick to coffee machine filters – Most of these will do the job required for a coffee machine, including removing the right stuff. Depending on the one you use, check the specifications
- Use a water filter jug – Want to play it safe and filter the water before it goes anywhere near your machine, or maybe you use another method to make coffee? There are plenty of jugs out there which have filters available to buy that make the water just right
- Buy a water softener – Hard water affecting other factors too, such as washing your hair or the dishes? Water softeners can be bought which filter tap water at the point of pouring. They sit under your sink out of the way, and are expensive to buy but often the cheapest option long-term
- Regularly descale – On top of the above, always use a proper descaler to clean kettles, coffee makers and machines to get rid of even the smallest of traces of minerals and keep everything in top condition. Most brands have dedicated descalers available.
Dan is a former competition barista and has been honing his knowledge of coffee for over two decades.
He has worked in coffee farms in Peru, as well as roasters in Australia. He now trains new baristas and hosts cupping experiences in Austin.