As a true coffee enthusiast, you have long studied the technical specifications before you bought the best coffee machine. Without wasting time and money you purchashed the best coffee beans. The importance of the quality of roasting and grinding is in your fingertips. Yet you feel like these are still not enough to experience a perfect and constant taste every day, sipping your steaming coffee

This fluctuation in quality is caused by the simplest ingredient, water.

When making an espresso, the parameters of water forced through the coffee gind like temperature, and pressure needs to be specified. During this process, nearly 1000 different organic and inorganic compounds are washed out, which are responsible for the taste and invigorating effect of coffee. When completely pure water, free of dissolved salts, is used in the preparation of coffee, certain compounds remain in the coffee, and thus the result obtained is far below expectations.

To make the perfect coffee, the water must contain salts, which influence the taste of the coffee in the following. The salts themselves change the taste of the water and the taste of the brewed coffee as well. Via ion strenght and ion exchange the dissolved salts change the number and amount of compounds that will be washed out from coffee beans, thus affecting the final result. If the water used to make coffee contains certain elements and their ions, such as chlorine, it can bring the coffee taste into a very bad direction through the before mentioned ionic strength and ion exchange processes.

The quality of tap water is constantly changing, both in salinity and in the amount of suspended particles. It is below the limit set by the regulations, but this value is always given as a range by technicians. Thus, in general, tap water contains too much solute that affects the quality of coffee. It is also important that tap water is always disinfected with chlorine, which adversely affects the amount of soluble coffee beans, so coffee brewed with tap water cannot come close to the best quality that can be extracted from the given coffee bean.

Ceramic Filters: The simplest filtering equipment to solve the problem of removing larger floating particles from the water, and it has only little affect on the ion content. Therefore we do not get perfect result when brewing coffee just as we don’t get we brewing with tap water. The only result of ceramic filtration is that due to smaller suspended matter content, the interior of our coffee machine is going to have less sludge.

Reverse Osmosis Filters: These filtering devices are capable of producing very high purity water, but do not result constant quality. A well-run machine can produce very pure, water with a few milligrams of salt per liter. This salt content is unfortunately not enough to dissolve the coffee in the ideal quantity and quality. It is important to note that if the quality of the incoming water changes, the quality of the water discharged from the purification system will also change. This can happen at any time with tap water (think of how many pipe breaks and how many times the amount of chlorine added to the water is changed). If the RO unit does not have a chlorine pre-filter, clhorine will stay in the water which can be fatal to coffee taste. Coffee made with such water will usually be empty and the crema will be thin

Water Purifiers with ion exchange resin: These are usually water softeners, cartridges that filter out certain ions from the water. Cafés mainly use this type of softener but in a flow-through system which is responsible for removing limescale that is harmful to the coffee machine.

When speaking about water purifiers in general we talk about cation exchange resin containing softeners. These purifiers filter out ions responsible for temporary water hardness, like Mg, Ca. The problem with these systems is that, not all the cations responsible for the formation of limescale should be filtered out, because they are actively involved in the coffee extraction process. The too much cation, even if only one type is present (eg NaHCO₃) in the water for coffee brewing will not open up all the flavour that is present in the coffee bean. It might also negatively affect our coffee flavour (eg sodium overweight). The taste of coffee made with such water is far from the coffee brewed with water of sufficient hardness and proper ions.