Yes, pure RO water can damage your espresso machine.

Water analysis, treatment, and mineral recipes for optimum taste and equipment health.

#1: Post by Parkeralto »

A little story from personal experience. I purchased a Quick Mill Alexia when they first came out; a great little single boiler E61 machine and from day one used RO water to fill the tank. All was fine until about six months in, the heating element went out. Chris's Coffee promptly replaced it on warranty; a year later that one went out. They replaced that one too. Another year, another failure. Now I had to pay for them and bought two more so I would have a spare. By now you would think I would have caught on but no; I decided I was a manufacturing defect and got very good at installing new elements. (They can be installed through the bottom without disassembling the machine) This was a high use machine; on all day every day and over a eight year period I replaced 5 heating elements which succumbed to pinhole leaks. The sort of upside, was that there was never any scale or other damage to the boiler or other metal parts that I could see from running pure RO. But I won't do that again.

It wasn't until I purchased a new ECM Technika that I learned of this well-known problem with RO. Then I tried the fancy German filter system that replaces calcium with magnesium but does not lower the TDS by much. After a year on that water, the mushroom in the Technika's E61 group was showing signs of scale. So now I am back on RO water with a remineralizer that takes the TDS from about 10 up to 36 or 40 with a neutral PH and so far so good. I am searching the forum for leads on good remineralizer cartridges. As I understand the science; water should have between 50 to 100 TDS, more magnesium than calcium for good espresso and minimal scaling.

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#2: Post by CarefreeBuzzBuzz »

I used to live in Marin. Why not take your RO water and remineralize it yourself. Don't use a cartridge. Is this new machine plumbed or a tank? The results with a cartridge will vary by age of cartridge and how long the water is exposed to it? If interested PM me your email and I'll send you docs.

Basically it's what I do with my tank on my cart system.

Espresso Cart - Goodbye Plumbed In
Artisan Quick Start Guide


#3: Post by Parkeralto »

This is a plumbed in machine; It is switchable but a plumbed install was one of my goals ;and my new Alex Leva in plumbed only. I am looking at a tankless RO system with reminalizer. It remains to be seen how that works out but at least I have learned to test my water frequently.


#4: Post by Ciaran »

I would argue that you don't have enough information about the quality of the water going into and out of the RO to make a general conclusion about the effects of RO water on equipment. Without such information, we can't even define the "purity" of the permeate water from the RO.

The specs for hardness you mention is more in line with larger ratios such as batch brewing or pour-over. Espresso extraction has much tighter ratios, and as such the mineral concentration has less effect.

Remin cartridges for home use, such as the Omnipure K2548 can get your post-RO water that is between 40-60ppm, depending on starting pH. Yes flow rate and contact have an effect, but with Calcite, it's not going to overcorrect. Corosex (magnesium oxide), on the other hand, will increase the pH and TDS dramatically. Most cartridges need to be flushed daily, as the first litre will have very high TDS.


#5: Post by F1 »

Wait WHAT? You were drinking espresso made with RO water for 2 years? The flavor must have been horrendous.


#6: Post by Nate42 » replying to F1 »

I had a friend who plumbed his machine into a DI system, so even worse. Never thought it was a good idea, but to my surprise espresso actually tasted fine. I think you just naturally learn to compensate in how you dial in your shots.