Why use RO?

Reverse osmosis is rapidly becoming the water treatment system of choice for speciality coffee applications. This is because reverse osmosis removes a high percentage of contaminants, including calcium and other dissolved alkalinity which determines the water’s hardness. Once this has been removed, the alkalinity can be dosed back in in a measured way, giving baristas and roasters total control over the hardness and mineral composition of the water they use to brew their coffee.

How Does It Work

Reverse osmosis works differently to carbon filtration, in which carbon absorbs contaminants from the water passing through it. Instead, reverse osmosis systems contain a semi-permeable membrane – basically an incredibly fine mesh. The water passes through the membrane, leaving almost all dissolved contaminants and impurities behind.

This has several benefits as it not only removes chemicals such as chlorine, which impart an unpleasant taste but also removes dissolved minerals such as calcium. This mineral content can form hard limescale deposits on the inside of your equipment and can also affect the extraction of flavour from your coffee beans.

The Scale of the Problem

If you live in a hard water area, you’ll have noticed the white, chalky lime scale deposits that build up inside your kettle. Limescale can not only break off and end up in your end product but, because it doesn’t transmit heat very well, it also affects the efficiency of the heating elements inside your equipment.

Though you may not be able to see it, limescale deposits will be building up inside the boiler of your espresso machine where it adheres to internal surfaces. Limescale can be removed with descaler solutions but these tend to be highly acidic, rendering them difficult to handle and dispose of. Repeated use of strong descaling solutions can also reduce equipment lifespan.

RO and Coffee

Reverse osmosis systems not only protect your equipment from the dissolved minerals that cause limescale but they are ideal for creating the perfect feed water for speciality coffee applications.

Speciality coffee is unusual in water treatment terms in that a certain amount of hardness in the feed water is desirable in order to obtain the best extraction of flavour from your ground coffee beans. Using feed water that is too soft generally leads to flat, flavourless coffee. Conversely, water that’s too hard or contains the wrong minerals can also negatively impact the taste of your coffee. The presence of chlorides or sulphates, for example can cause coffees to become excessively bitter.

To get the best flavour from your coffee therefore, you need to find the ‘sweet spot’ with a water profile that is neither too hard, nor too soft.

Made to Measure

Water hardness or TDS (total dissolved solids) is measured in PPM – parts per million. A low cost TDS meter will help you determine the TDS of your local water and can also be used to ensure your reverse osmosis system is supplying feed water with the most beneficial level of TDS.

According to the Specialty Coffee Association of America (SCAA), the optimum ppm for feed water in speciality coffee applications is around 150ppm, though anything between 75 – 250ppm is within an “acceptable range”.

Obtaining exactly this level of water hardness is tricky given the wide variation in water hardness levels across the UK. Some sites, in Devon for instance have very soft water, with low TDS while London has some of the hardest water in the country with up to 600ppm in some areas. The hardness of mains water can also vary even to a single site, depending on the nature of the rocks that the water has passed through before municipal water treatment.

By removing the majority of dissolved minerals and then dosing alkaline minerals back in to the feed water in a controlled manner, the perfect water profile can be created regardless of your geographical area and local water type.

Blending In?

The speciality coffee industry has embraced reverse osmosis to the extent that manufacturers are now producing systems specifically for this market. The Pentair Everpure Conserv 75E for example, feature a special blend valve, allowing operators total control over the exact mineral content of their feed water. The blend valve works by allowing a certain amount of water to bypass the R.O. membrane, this retaining a small amount of dissolved mineral content. Cleverly, the system also comprises a carbon filter and a scale inhibitor which treats all the feed water regardless of the bypass setting. This ensures that even though some mineral content has been retained, it is ‘inhibited’ to prevent limescale forming inside your equipment. The best of both worlds!

Is Reverse Osmosis for You?

In order to determine if reverse osmosis is that best method of water treatment for your site conditions it’s best to get your water tested. It’s then recommended to consult an expert with the results as well as with your expected water usage (i.e. the number of cups of coffee you’re producing per day).

Your local water hardness and required capacity will then be used to determine whether reverse osmosis is the best method and if so, which is the best system. Espresso Solutions stock a range of reverse osmosis systems from 3M, BWT, Pentair Everpure and European WaterCare, allowing them to always supply the right system for any given combination of site and capacity requirements.

For more information, please call 01293 769 825 or email [email protected].