The Dangers of Distilled Water in Boilers: Fact or Fiction?

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Vice Connoisseur

#1: Post by Vice Connoisseur »

Dear HB Espresso Lovers, Hobbyists, and Mad Geniuses,

Regarding water use and setup of the Elektra Microcasa Semiautomatica (my very recent impulse buy--woohoo!), this suggestion from the buying guide makes a lot of sense:

"I do have one suggestion-initially fill the boiler with reverse-osmosis (RO) or distilled water. The boiler fill is manual, so no minerals are required and the RO or distilled water will never scale. Since the boiler size is ample and does not need to be constantly refilled, it can be done whenever the water tank empties, again using a few ounces of RO or distilled water. If you do this, you can use the best tasting, neutral or moderately hard water for making espresso, and descale the group and heat exchanger just like any other home machine without having to worry about the sealed boiler."

However, in scouring espresso info sites, I keep coming across cautionary statements warning that RO/distilled water can "leach" metal ions from boilers (brass and copper were specifically mentioned--the Semiauto's is brass) and actually cause damage. Preventing boiler scale is great, especially when I can simultaneously use water with whichever ions I prefer for great-tasting espresso & decrease maintenance hassle, but obviously not if the end result is detrimental to the machine. I've read more pages than I care to admit about water & espresso-making, and still am not totally clear on this point (but do feel like I have a better-than-average idea of how pH, TDS, and various ions affect the flavor and body of my morning beverage....I think this site has already created a monster in less than a week).

So is this rumor true, or Machina Urban Myth?

I've noticed that there are several of you on these threads who have an impressive grasp of chemistry as it relates to caffeinated beverage-making....can anyone confirm or refute the "dangers of distilled" theory?



Proud (read: Obsessed) New Elektra Owner

Vice Connoisseur (original poster)

#2: Post by Vice Connoisseur (original poster) »

Shoot! I actually *did* search for this topic, with no direct result....until I posted, at which point a thread with this exact question came up.

Will distilled water harm my Elektra Semiautomatica?

Incidentally, the answer is undecided, but mostly of the "probably don't use straight distilled" variety.


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#3: Post by algue »

Hi monster :D
Welcome on board
Solution processes are equilibrium processes. Equilibrium means that an element or a chemical species will dissolve in water with a speed depending on its concentration in the water. The lower the concentration, the higher the speed.
During the solution process the speed will decrease so much that from a given time the concentration of the chemical species will not increase anymore. That concentration is the equilibrium concentration of that chemical species at a given temperature (and is a sort of constant).
Knowing this, I think that should be evident that chemical species will dissolve more in distilled water, as they have to reach their equilibrium concentration at that temperature and the initial concentration is close to 0.
Absolute quantities are small, though.
This could be an issue only over relatively long times.

Vice Connoisseur (original poster)

#4: Post by Vice Connoisseur (original poster) »

I understand those concepts, and your answer makes sense. Thank you!

So, correct me if I'm wrong, but it could be summarized that in theory, over long periods of time, distilled water could potentially cause loss of metal ions/material if in constant contact with metal (brass, copper) components, but it may or may not be significant enough to disrupt the proper functioning of the machine....i.e., use at your own (in all practicality, probably minimal) risk.

I suppose that in theory, one could alternatively use non-distilled water with low-scaling mineral/ionic content and only rarely need to descale the boiler, but avoid any theoretical issues with leaching/pitting of the brass components by distilled water.

Thanks again! Now I won't have to fret about my precious, precious boiler :wink:

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Team HB

#5: Post by another_jim »

The water in the boiler will leach metals; and distiiled or RO water will leach more metals than water with minerals. But since the Semi uses the boiler only for steam, not for coffee water; it is not an issue in terms of taste or health.

How about equipment life? Here you have a trade off between corrosion and scaling. Distilled water corrodes; hard water scales. In the steam boiler, it's water + minerals in, and steam, no minerals out. So any minerals you add will build up over time. If you don't introduce any, some will build up anyway due to the leaching of the metal ions. In other words, the corrosion ends as the minerals build up. But if you use hard water, it will scale up the heating element and pipes

You can drain the boiler, something that you might want to do once or twice a year regardless of the water you use, by turning the machine on its side, when it's cold, and opening the steam valve, so water runs out. There is a valve at the top, called the vacuum breaker, which is open while the machine is cold, so air can enter and let the water will flow out.

(Obligatory message to all newbies) For full enjoyment, buy a good grinder (I see you have the Vario which is great), and use good coffee.
Jim Schulman

Vice Connoisseur (original poster)

#6: Post by Vice Connoisseur (original poster) »

Excellent and articulate explanation, Jim. Thank you!

Re: Newbie suggestions....I think you guys have really excellent, consistent input for the priciples of Home Barista Newbie Formula for Success (eg., get a decent grinder, use fresh coffee, do whatever you want, but don't say we didn't warn you first, etc)....I have high hopes for my new and improved beverage-making equipment!

After spending a good (actually, embarrassingly copious) amount of time reading suggestions for a starter setup, I decided on a Baratza Vario (last minute over a Mazzer Mini--my usage is relatively low, so don't probably need the longevity of a semi-commercial machine, & I think I'll appreciate the Vario's size and convenience factors), and there are roasters nearby where I can get fresh beans. Just for a reference point, I'm going to start with Intelligentsia Black Cat & go from there.

After my initial "Wow, so this won't be a mere kitchen appliance outlay of cash....more like a home appliance outlay," I sucked it up, determined that I still wanted to be able to make a decent espresso, no matter how bougie the purchase would come off to my friends and family (whatever...they'll benefit from my bougie-ness!) and after hours of research and comparisons, was all decided on an ECM Technika IV....and then, I just couldn't help the last moment, aesthetics won out. I never thought I could be obsessed about something sitting on my kitchen counter....but the Elektra, she is a thing of beauty.

Thanks for all of the deliciously useful information!! I'll be putting it to the test, and hopefully happily caffeinated as I traverse the Newbie Learning Curve.

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#7: Post by algue »

Talking of Semiautomatica, don't forget to read Jim's review on this site.
It's a must.


#8: Post by C6H8O3 »

I use an ion exchange water softener and activated carbon filters for my machine. My water post filtering is 0 GPG. I recently inspected my E-61 machine's mushroom after one year of use and found no scale. Impressive as our water from the tap is 15 GPG.

My ph is 7.2 - so it is not acidic. The inside of the heat exchanger copper tubing (from what I could see) was a nice oxidized brown - so no etching is going on.

Chris Coffee sells an ion exchange water softener, or you can buy the components here: ... ridge.aspx ... icron.aspx

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Team HB

#9: Post by cannonfodder »

I just keep a chunk of lead in my water tank so it corrodes rather than the brass. :mrgreen:

But in all seriousness, you do need some minerals in the water to get a good extraction. Too soft and it will be thin, bland, and lifeless with little mouth-feel. I would think pure distilled water would not give you a good shot but filtered city water will still have some trace elements in it with very low hardness which would prevent scale buildup. You could also take bottled distilled water and add a little tap to it to increase the hardness.

Either way, the machine will last decades with proper care.
Dave Stephens

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#10: Post by damonbowe »

Distillers water over extracts and ruins the coffee.