It’s true that the choice of coffee bean is the most important ingredient for influencing the flavor of your coffee, but there’s no doubting the importance of water – the ingredient that makes up around 98% of the drink.

There are lots of different factors in play when it comes to water – with the type of water affecting if the bean is over or under-extracted, leaving the flavors either ‘too bitter’ or ‘too sour’. On top of this, it’s also worth considering:

  • Water hardness
  • Water PH
  • Water contaminants


Below, we look at how these different factors influence your brew and what you can do to avoid each issue.

Water Hardness

Water hardness refers to the number of ‘hard’ minerals in your water supply (mainly calcium and magnesium), which can cause limescale to form when the water is heated up. If you’ve ever notice white, chalky deposits on your taps or kitchen appliances, you probably live in a hard water area.

Water is classified as being ‘hard’ if its total dissolved solids (TDS) exceeds 180 parts per million (ppm). These minerals occur in all types of tap water, so a level of around 50ppm is still considered soft water.

The Speciality Coffee Association of America have even specified the perfect level of water hardness for brewing coffee at 150 ppm , although between 75 to 250 ppm would still be useable.

However, certain minerals can actually positively influence the taste of coffee, meaning that overly soft water is also negative in the brewing process. These minerals present in hard water are known as cations. Without getting too technical, cations are positively charged ions which have been found to be crucial in extracting the flavor of the coffee bean.

If you think water that is too hard or soft is affecting the quality of your brew, you can buy a basic TDS testing meter to see the levels of dissolved minerals in your water.

PH Levels

The PH level is another factor that can influence the taste of your water. PH refers to the acidity and alkalinity of water. A low pH (pH 6.5 or less) indicates acidic water and a higher pH (pH 7.5 or more) means the water is more alkaline.

Coffee brewing is based around finding a balance between the bitter and sweet tastes of the coffee bean. If you find that you’re struggling to find the ideal balance between the sour and bitter tastes resulting from the brewing process, water acidity could be the cause.

A pH between 6.5 and 7.5 is still acceptable for coffee brewing, although alkaline water will affect the extraction resulting in a ‘flat’ taste. If the water is too acidic the coffee will be too bitter.

You can easily buy a pH tester to determine your water acidity, then if there are any abnormal results, contact your water supplier or consider investing in a water filtration system.

Water Contaminants

There are some particles and chemicals that you don’t want in your water supply and ultimately your coffee. Here we list the elements you definitely don’t want in your brew!

Iron and copper

Water can pick up iron and coffee in old piping to your home or commercial premises. These elements will give your coffee an unpleasant metallic taste, so best filtered out.

Carbonates, bicarbonates and hydroxides

These ions can make your water more alkaline, thus leading to flat, lifeless tasting coffee. They can also form scale on your appliances including your coffee machine.


Chlorides present in your water supply can corrode stainless steel and other materials present in water-fed appliances. If you have corrosion on your coffee machines, this could be the cause.


Sulphates can make brewed coffee taste more bitter, and when combined with calcium in calcium sulphate, form scale on brewing equipment.

Is Water Treatment the Solution?

Whether you are a coffee enthusiast who obsesses over their home brew or a professional coffee maker, there is no doubt that water quality massively effects the taste of the final coffee.

Run a test brew using bottled water and see if you can taste an improvement. If so, it could be worth treating your water.

There are various different filters available which can filter out some of the less desirable elements mentioned above.

One treatment method is rapidly growing in popularity in the coffee industry is reverse osmosis. These types of filter use the process of reverse osmosis to pass mains water through an ultra-thin membrane, resulting in almost 100% pure water.

Once you are certain the water you are using is (almost) pure, you may want to adjust the amount of minerals using blending valves. Many of these filtration devices come with blending valves, which allow you to let small amounts of beneficial minerals into your coffee, giving you much greater control over the type of water you’re brewing with.


While coffee beans have been analyzed in forensic detail for some time, people may have missed another vital ingredient – water!

If something is not quite right about your coffee brewing, consider how hardness, acidity and contaminates may be affecting flavor.

If you want to make the perfect coffee, you need to get scientific and test your feed water for some of these issues. If you suffer from some of the issues mentioned above, you may want to consider a water filtration system such as a reverse osmosis system.

Matt Pavli

Matthew Pavli is a content writer at Aqua Cure – a supplier of water filtration systems for domestic and commercial premises. Aqua Cure supply a wide selection of specialist water filters and treatment devices to deal with a range of water quality issues. Alongside his work blogging about water quality on the Aqua Cure blog, Matthew can be found playing and watching sports such as football and basketball in the North West of England.

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