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.

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

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.

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.

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

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.

Ciaran wrote: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.

Interesting. I've read hundreds of posts here about proper mineral concentration for espresso, and of course I've read Jim Schulman's Insanely Long Water FAQ. This is the first time I've seen an assertion that mineral concentration has less effect on espresso than brewed coffee. Do you have any sources for this conclusion or is it your own?

I'm not saying it isn't true. Nate42 suggests that you simply compensate for low mineral content by changing dialing-in parameters. That makes sense, though I'd prefer to see some EY measurements comparing RO and water with recommended hardness. And my own experience is that removal of all hardness by my cation system hasn't made espresso extraction any different than my old Claris Everpure system adjusted to 70 ppm. I've always thought that either the salt ions or remaining alkalinity minerals, which are still high, took the place of hardness in extraction. But maybe it's just me dialing in higher extraction.

Anyway, if true, the notion that mineral content isn't important for espresso extraction would be news to most of HB's members.

Parkeralto wrote: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.

Bumping this back up as I am looking for the same solution for my Linea Mini that is plumbed in. Moved to South Florida recently so am hoping to ditch my cobbled tank R/O with mixed filtered tap water that worked for me in LA to a tankless with remineralization. The city water report doesn't even mention Chloride levels, but I think I'm safe to assume they are high. Has anyone considered the Frizzle? https://www.amazon.com/Frizzlife-Revers ... merReviews

or perhaps another tankless variety with a BestMin cartridge plumbed in before the machine? (would closely match LaMarzocco's RO system)

Main question is flow pressure from these being adequate to push through additional remineralization cartridges and still being sufficient for the Mini.

Peppersass wrote: Nate42 suggests that you simply compensate for low mineral content by changing dialing-in parameters. That makes sense, though I'd prefer to see some EY measurements comparing RO and water with recommended hardness.

Don't get me wrong, I wouldn't advocate for RO or higher purity water in espresso, if nothing else because of the risk of long term damage to your machine. I wouldn't go so far as to say there's no impact on extraction either, don't have the data either way. What I would say though is the idea that its automatically going to taste like garbage if you use high purity water just isn't true: we pulled a lot of good shots on that machine. Could they have been better? Quite possibly. But they were still good.

Here's what I think would be an informative test if someone with a refractometer and less lazy than me has the inclination:
- Dial in an espresso with a standard water profile to taste, and measure extraction yield.
- Change water to high purity with no other variable change, compare taste and measure extraction yield. I'm sure you will see a change to the worse here.
- Re dial in to taste with the high purity water, measure extraction yield yet again. I bet you can get at least part way back to where you started.

Easier said than done, but would be interesting if someone wants to take it on.

F1 wrote:Wait WHAT? You were drinking espresso made with RO water for 2 years? The flavor must have been horrendous.

Is there a study that shows RO water gives horrendous flavor? Genuinely interested. I understand the SCAA, Schulman, Rao, et al. water recipes have some hardness. But I also see contradictory opinions and anecdotes like the popular rpalvis water here and a study like this that suggests soft water is just fine, maybe even better than the most, as far as tastes go:

Nate42 wrote:...What I would say though is the idea that its automatically going to taste like garbage if you use high purity water just isn't true: we pulled a lot of good shots on that machine. ...

That's what I found as well. When I switched from a pump machine to Robot, I kept using my own Barista Hustle water (85GH/50KH using ZeroWater + magnesium sulfate and sodium bicarbonate) for a couple of months. Because corrosion is not an issue with the Robot, I wanted to simplify my setup further and tried just straight ZeroWater (i.e. RO-equivalent) and could not discern much difference in taste. So I've been using it happily since then. It's really nice not having to mess with the GH/KH concentrate.