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Water Filtration for Coffee

It is an ancient wisdom that good food is cooked with good ingredients. Likewise, the perfect coffee is brewed with perfect water. Water is more than two hydrogens and one oxygen molecule. It is a clear canvas on which coffee flavor notes make a mark. 

What makes water impure?

The water falling from your tap carries a load of chemicals and sediments. They can change the taste, smell, and color of your coffee. A giant culprit is a chlorine; it disinfects the water and leaves your coffee smelling like a swimming pool. Next in line is the rotting stench of bacteria and the egg-like stink of hydrogen sulfide. Coursing through rusting pipes and taps, water carries the reddish-orange tint and metallic taste of copper, iron, and other heavy metals. Particles of dust, sand, and silt make the water cloudy. 

What kind of water does coffee need?

The Specialty Coffee Association has standards for water temperature, water to coffee ratio, grind size, and contact time. Add to that, the standards for quality of water, and you have the SCA’s Golden Cup Standard for brewing. There are 4 parameters of water quality- hardness, pH level, sodium, alkalinity, and total dissolved solids. Apart from these, no smell, color, or chlorine should be present in the water. 

Hardness

The hardness of water depends on dissolved compounds in the water like calcium and magnesium, and sometimes aluminum, iron, copper, and lead. As the mineral levels rise, a chalky crust called limescale starts to grow on the inner lining of the equipment. Pipes choke up, stop working and cost heavy repairs. Ideally, 17 to 85 mg per liter is the calcium hardness range for brewing coffee and espresso. Low calcium content helps bring out the flavors. 

pH Level

The pH level depends on the concentration of dissolved hydrogen ions in the water. It affects the solubility of water. The pH scale ranges from 1 to 14. Both extremes are bad for the water; too acidic is bitter and sour, and too alkaline is bland. Coffee lies at a pH level of 5, somewhere on the acidic side. For the water, a neutral level of 7 is ideal. 

Sodium 

Most water supplies contain sodium because of the water softening process. If the water is too soft, the excess sodium can harm your machinery. Moreover, it interferes with the experience of sweet fruity, and chocolate flavors in coffee. Ideally, coffee should be brewed in water having 10 mg/L of sodium.

Total Alkalinity

Total alkalinity is the water’s ability to neutralize acid, also called ‘buffering capacity. It measures the concentration of dissolved alkaline substances from carbonate, bicarbonate, and hydroxide compounds. Absorbing these ions prevents the water from becoming acidic, and keeps the pH level stable. If the alkalinity is too high, it becomes difficult to extract flavors while brewing. If it is too low, the water becomes acidic. As per SCA standards, at or near 40 mg/L is the ideal range of alkalinity.

TDS (total dissolved solids)

Dissolved solids are minerals, salts, metals, ions, and organic and nonorganic matter dissolved in the water. Pollutants, fertilizers, road salts, and pesticides harden and contaminate water. As per SCA standards, 150 ppm (parts per million) is the ideal TDS level of brewing water. Regular drinking water, somewhere around 300-500 ppm, is too hard for brewing, while water with 0 TDS is too flat. 

Water treatment methods

It may seem like the best way to go is to filter out all minerals and soften your water so that both your coffee and your equipment remain unscathed. But the reality is that some minerals are actually favorable to brewing and excessive softening can bring too much sodium. Different treatment methods work on different aspects of the filtration process. Let us look at how each one works.

Mechanical filtration

Mostly used as a pre-treatment filter, a mechanical filter is made of synthetic foam, nylon floss, or materials as such. The filter collects particles of debris and sediment but allows finer microns to pass through. It ensures that these particles don’t overwhelm the other filters in order. 

Carbon filtration

Carbon filters have activated carbon that absorbs chlorine, trihalomethanes (by-products of disinfecting by chlorine), organic compounds, and contaminants like lead and asbestos. They remove foul smells and tastes from water. 

The filters are made of either wood-burned carbon granules or charred coconut shells. They come in blocks or granules. Blocks have a good surface area, while granules ensure quicker flow. You can install the filters in your water supply line or in front of your brewing equipment.

Carbon filters are great for eliminating chlorine. They keep minerals that enhance the brewing process. One drawback is that they don’t remove chloride and chloramine. The filters have to be replaced every 6-12 months depending on the size of the equipment and daily water use. Past their recommended lifespan, they can contaminate the water with activated carbon, which has harmful side effects.

Scale inhibitors

A scale inhibitor, as the name suggests, protects your coffee and espresso equipment from forming scale. As mentioned earlier, scale is formed by excess mineral and alkaline deposits on the inner lining of equipment. It spoils machinery and slows down work. A scale inhibitor is a magnetic or electric device that prevents these minerals from bonding and building up on the walls of your equipment.

Ion exchange

In this treatment, contaminants like calcium and magnesium ions are exchanged for sodium ions to soften the water. The only principle is that the contaminant and the exchanged substance have the same electrical charge (positive or negative). Ion exchange works well for espresso machines, but not for filter coffee

Reverse osmosis

Reverse osmosis targets total dissolved solids to an extent that all minerals are eliminated from the water. The problem is that some dissolved minerals like calcium and magnesium are necessary for bringing out floral and herbal flavor notes in coffee. Reverse osmosis can also bring down the pH level of the water up to 5 or 6, which can turn your coffee sour. If you are using reverse osmosis, you might want to re-treat the water by adding minerals and alkaline-rich media. You will also need a large storage tank, a drain for wastewater, and a robust electricity supply. 

Third wave water

Third Wave Water began with a Kickstarter campaign in 2017 and was later popularised on Shark Tank. It is a mineral supplement that adds natural minerals and balances pH. As mentioned earlier, minerals like calcium and magnesium enhance the flavors of coffee. Third-wave water does exactly that: it raises the mineral, TDS, and sodium levels of the water to SCA standards without chemical additives. But the water must be de-ionized, distilled, or undergone reverse osmosis. While Third Wave Water is not feasible for commercial enterprises, it is suitable for office and home settings.

Now that you have seen all your options, you have a lot of information to process. You can start by conducting a water test to know the composition of your water. Look at where your water supply is coming from and what kind of equipment you use. If there are obvious issues with your water quality, you can nip them in the bud. Moreover, you will end up saving costs on features that you don’t need. The best choice depends on your water quality, pressure, and flow rate. A good brew comes from good water, and good water comes from the right research.

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