A great cup of coffee starts with great water. The coffee you’re drinking contains somewhere between 90 and 99 percent water, depending on whether it’s an espresso or a filter coffee. Getting the water right is essential for brewing sweet, juicy, transparent coffee. Getting the water wrong, however, can lead to flat and dull-tasting coffee, equipment breakdowns, and even health hazards for you and your customers.

The quality of your water, and hence the quality of your coffee, is determined by the water filter that you use. All mains water needs some kind of filtration to be suitable for coffee brewing, but exactly what kind of filtration system you need depends on what is in the water from your tap.

his chapter has two parts: First, we’ll explain why filtration is so important, both for your coffee flavor, and to protect your espresso machine.

We’ll then give you more details on what is happening inside your water and why it might be worth learning to test your water yourself to get the most out of your coffee.

Protect your equipment

The most important reason to filter your water is to protect your espresso machine. The machine is often the biggest investment a cafe has to make, so it’s important to look after it well.

Without filtration, hard water can cause limescale to build up in the boiler, especially on the heating element. As the heating element gets covered in limescale, it becomes less good at transferring heat to the water.

Each millimeter of scale makes the boiler up to 10% less efficient. Not only does this waste electricity — and therefore increase your energy bills — but because the heating element has to work harder to heat the water, it becomes more likely to overheat and burn out.

Limescale build-up can also block the flow of water through the espresso machine. Even a small amount can sometimes be enough to completely shut the machine down.

Limescale can therefore be very damaging to the machine, and your business. Removing it from a commercial espresso machine can be an expensive procedure — so it’s important to filter the water to stop limescale from building up in the first place.

Boost flavor

As well as damaging your machine, hard water can affect the flavor of your coffee. Without the right filter, your coffee can end up tasting chalky or flat.

A good water filter also removes any chlorine and other contaminants in the water. A small amount of chlorine might not taste bad in the water by itself, but it can react with compounds in the coffee and produce unpleasant, chemical-tasting flavors.

Chlorine and any off flavors in the water are easily removed with an activated charcoal filter. A good water filter will have an activated charcoal layer built in.

One thing water filters are not designed for, however, is removing microbes. If there is any risk of bugs in the water that could harm your customers, then the water needs special treatment, such as UV light, to remove these first. In Riyadh, the drinking water supply is generally safe, but sometimes the water in individual buildings can be contaminated if tanks are not properly maintained.

What type of filter should I use?

Which system is right for you will depend on the water in your building, but also on how busy the cafe is, and other practical considerations.

There are a lot of different water filters on the market, but they fall into three general categories.

  • Simple water softeners that you can regenerate by adding salt — similar to the kind you find in dishwashers. These are fine for dishwashers, but we don’t recommend them for specialty coffee shops.
  • Filter cartridges, such as the 3M ScaleGard system. These are simple to install and can produce very good results — as long as you choose the right cartridge for your water.
  • Reverse osmosis (RO) systems, such as this compact unit from Everpure. These are more expensive to install than filter cartridges, but often work out cheaper in the long run.

If the water doesn’t have much limescale in it, then you might only need a simple carbon filter to remove chlorine, which can be very cheap. If the water is particularly bad for coffee, then a more expensive reverse osmosis system is sometimes the only option.

To make sure that you get the best water treatment for your cafe, we recommend talking to your espresso machine technician about your needs. They should test your water, and based on that test they can recommend the best system for you.

For most cafe owners, this is all the basic knowledge that you need. But if you want to know more of the technical details about what is in your water and how it affects your coffee, then read on.

What’s in your water?

No matter how good your tap water is, it’s never one hundred percent pure. All drinking water naturally contains dissolved minerals.

Water dissolves minerals when it comes into contact with rocks in the ground, Paragraph - Bold so the exact composition of minerals in the water depends on the rocks and soil in the area the water is drawn from.

The most common mineral found in drinking water is calcium carbonate — which comes from chalk or limestone dissolved in the water. At high temperatures, for example inside an espresso machine, the calcium carbonate becomes less good at dissolving in water and starts to form a solid layer called limescale.

Hard water has more of these minerals in it, so is more likely to form limescale, while soft water has less. Some of the minerals are needed to brew a good cup of coffee, but having too much, or the wrong kind of minerals in your water can be bad for the coffee and bad for your equipment.

If there are not enough minerals in the water, on the other hand, the water can be corrosive and gradually eat away at parts of the machine. Corrosion can be particularly severe if the water contains iron or chlorides. Corrosive water is also more likely to dissolve lead and other heavy metals into the water, which presents a possible health hazard to your customers.

The ideal water for coffee is soft, but not too soft. The right filter solution will remove excess minerals to prevent limescale from building up but keep a controlled level of minerals in the water to eliminate any risk of corrosion.

Enhance your coffee

The minerals in the water also play a role in the extraction of the coffee and can have a considerable effect on the flavor. The minerals to pay attention to here are calcium, magnesium, and bicarbonates.

Calcium and magnesium minerals together make up what is called General Hardness (GH). They help the water to draw flavors out of the coffee, so a certain amount is necessary for great-tasting brews. Too much of these, though, and the coffee starts to taste heavy and chalky.

Calcium and magnesium seem to bring out slightly different flavors, so some water filters also aim to change the balance between calcium and magnesium to tweak the flavor of the coffee. Exactly how this works is still being debated.

Bicarbonates, meanwhile, are what make up Carbonate Hardness (KH), also called alkalinity. Bicarbonate balances out some of the acids in coffee, preventing it from being too sour. If there is too much bicarbonate, however, the acidity is lost and the coffee becomes flat and muted. The level of KH is also what mostly determines how much limescale the water forms.

The right filter solution will ensure the water has a balanced level of General Hardness (GH) and Carbonate Hardness (KH) to get the best flavor, but without allowing limescale to form.

Finding a balance

The water filter needs to create a balanced level of minerals in your water — both for coffee flavor and to protect your machine. What system to use, therefore, depends on what is in the water coming from the mains.

The mineral content of the water can vary even from one building to the next — for example in Riyadh, the general hardness (GH) varies between 120 to 600 parts per million (ppm), while the carbonate hardness (KH) falls anywhere between 25 and 250 ppm.

Espresso machine technicians will often fit the same generic water filter to every machine, to just protect against limescale. If you want the best flavor, though, you’ll need to test the water you get and adjust the filter to give you the optimum level of minerals.

Fortunately, testing the GH and KH in your water is fairly easy, using test strips or drop tests designed for measuring the water in aquariums, which you can buy in specialist pet shops. Measure the water as it comes out of the filter, and then adjust the filtration system as needed to get the right levels of minerals in your water.

According to the Specialty Coffee Association, the ideal water for brewing coffee has a KH between 40 and 70 ppm, and a GH between 50 and 175 ppm. This implies that in some areas of Riyadh with fairly soft water, the mineral levels are already fine, and the water only needs a carbon filter to remove the chlorine and other contaminants. In other parts of Riyadh, though, the water is very hard and will need to be treated before it can be used for coffee.

Once your filtration system is installed, keep testing the water regularly to make sure that the system keeps on delivering the perfect water for your coffee: your customers, and your machine, will thank you.

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