The Lowdown on Distilled Water

A common inquiry we receive is in regard to the type of water customers should use in their coffee making equipment. Some folks think that distilled water will be their best bet, as they won’t have to worry about scale build up or performing descaling procedures for the life of the machine. While there seems to be as many supporters as there are detractors regarding whether or not it’s healthy for the human body, we do know that distilled water is not healthy for your machine. Seriously!

First up, let’s talk about your equipment. Putting water that has a lack of ions or mineral content through equipment that is basically composed of minerals (stainless steel, copper, nickel, brass, etc.) means the water will take that opportunity to take on ions from the surrounding space, contributing to a slow breakdown of those materials. It will essentially leach minerals out of the metal components and degrade the machine’s performance over time. Additionally, there are several models of machines on the market (such as the Rockets) that use a minor electrical charge to determine if there is water in the reservoir. If there aren’t enough minerals in the water to conduct that charge, the machine’s sensor will report that the reservoir is empty.

Now, let’s talk about the coffee. The Specialty Coffee Association of America performed extensive testing and found that the ideal mineral balance is 150 parts per million (ppm). Coffee produced with water that contains this level of hardness is better balanced and a smoother cup. A lower mineral content allows for too much available space, often resulting in an overextraction and a bitter flavor. Conversely, water with a higher mineral content won’t have enough available space, so coffee will be underextracted and possibly more sour. As distilled water has hardly any mineral content (roughly 9ppm), using it for coffee preparation will result in a bitter cup.

We often say that you should use water that you like to drink to make your coffee — after all, coffee is over 98% water. Another option is to use softened water, which encapsulates the minerals, maintaining their structure within the water while prohibiting their ability to adhere to internal components. This can give you the best of both worlds: A smooth and balanced cup of coffee while also reducing the overall maintenance for the life of the machine.

6 comments for “The Lowdown on Distilled Water

  1. John Parkinson
    April 7, 2012 at 10:28 am

    I use distilled water as part of the cleaning process (after running Cleancaf or Durgol) through my Technivorm. Now I wonder if this is also a bad idea. I use bottled mineral water for coffee. Yum.

    By the way, really enjoy the videos!

    • Kat
      April 9, 2012 at 9:35 am

      Well, I would suggest that you rinse with the mineral water; even though you’re using a minor amount of distilled water in the system, it will slowly leach minerals from the metallic internals over time … and could have a minor adverse impact on the machine’s lifetime performance.

      - Kat

  2. Keith Wonderly
    September 18, 2012 at 6:04 am

    I have to disagree with the degradation theory represented in the blog. running distilled water through components will not rob ions from those components. Water likes to be balanced in its natural state and this means that distilled water, which is low on ions, will try and add ions to itself to achieve that goal. the distilled water will grab ions from everything it touches that can be dissolved or absorbed. The components inside your coffee maker are not made from anything that could be dissolved or absorbed. Heating tubes are generally constructed from aluminum tubing, and the tubing and misc valves are typically constructed of ABS plastic. neither could be dissolved by the distilled water.

    • Kat
      September 19, 2012 at 9:07 am

      Hi Keith -

      Thanks for sharing your opinion. The majority of machines we sell actually feature copper or brass boilers and distilled/deionized water does pit them over time, as well as having an adverse affect on heating elements. I agree that distilled water won’t have an impact on waterworks that are largely constructed of plastic, but for the majority of the home and commercial machines we sell, it does. Also, it doesn’t produce a balanced cup of coffee so we can’t recommend using it for that reason alone :D

      Best,
      Kat

      • Peter Lee
        May 23, 2014 at 1:27 am

        Your anecdote regarding distilled water causing more “pit” in copper or brass boilers is flawed. Both copper & brass (copper +zinc) tarnish & develop a patina when exposed to ANY kind of water H20 at the surface level, but distilled water nor any other would not “pit” them, nor damage them meaningfully over even hundreds of years. The damage is from the SITW, not the water itself.

        The oft mentioned “studies” purporting to reveal that “water for coffee should have a TDS of about 150ppm” is pseudoscience garbage based on subjective grading of taste scores – votes & surveys are not science. TDS or even conductivity are only gross measures showing that “something” is in there – it could be minerals like calcium, phosphorus, sodium, etc. But it could also be and often are things like heavy metals, radioactive substances, pharmaceuticals, microbes, and other SITW. For whatever reason, some people may prefer the taste of water that smells of garbage & pollution, but it certainly isn’t better for you and there are NO STUDIES of scientific merit that shows detrimental caffeine extraction rates with distilled or deionized water over polluted tap or mineralized water. In fact there are many meritorious studies showing the benefits of using distilled and deionized water in maximally extracting caffeine compared to “tap” water or other nonpure water (j.foodchem.2008.07.033 among many). If you feel pure water (R/O,D/I, distilled) makes coffee bitter by overly extracting caffeine compared to using unpure water, simply reduce the extraction times – it makes coffee faster then. But in fact this is another myth – pure water does NOT make coffee bitter, as anyone who uses 0 conductivity water can tell you. 0 conductivity water can only improve coffee brewing, not make it worse – one of these days nonscientific bodies like the National Coffee Association and others will get this topic right, once their preconceived biases based on opinions of so-called coffee experts are laid to rest.

        • Jack Denman
          October 2, 2014 at 3:44 pm

          To Peter Lee,

          Thanks for a good explanation. It goes without saying that distilled water will lengthen the life of the machine that will never need cleaning. The buildup of Calcium and Magnesium salts from anything but distilled water will clog the machine and make necessary the cleaning with corrosive chemicals that can and will pit metals and is not completely effective is removing it all without complete disassembly which owners will not do.

          You have exposed a bunch of old wives tales.

          Jack Denman

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