Is RO water the best for espresso?

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

#1: Post by Leopoldo95 »

I live in a hardwater area in the Midwest.

When I first got into espresso-making, I noticed that it didn't taste the best and tried it with some store-bought bottled water and the change in taste was quite noticeable.

I have tried many cheap water filters such as Brita and Zero Water, but have not been satisfied with the results.

I recently purchased an under-the-sink RO system (this one: ... UTF8&psc=1) and it has definitely improved the taste.

Would this be the optimal in-home solution for water? Or is there something more out there that I may not be aware of?


#2: Post by coolguy121 »

I would personally not be comfortable putting pure RO water on most espresso machines (maybe they're fine?) for personal fear of corrossion & bad tasting espresso (yes this is a legit fear of mine).

Try to look for water recipe such as RPavlis, or even customized GH & KH.

I personally don't find them to be too different from each other, at least not at pourover level with higher water content. RPavlis is usually the standard used by users who aim to wait as long as possible [e.g. never] to descale on the believe that descaling without taking apart boilers and pipes will do more harm than good.

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#3: Post by homeburrero »

I think it's worth pointing out that the particular RO system that the OP linked includes a remineralization cartridge, so it's not the same as pure RO. That remin cartridge adds more than enough minerals for the water level sensors to work and also bumps up the alkalinity to help with corrosion risks. You do want to replace the remin cartridge at the recommended intervals.

The output from that system would be a little different than rpavlis recipe water. The alkalinity would be a little lower and the calcium hardness would be higher (rpavlis has zero hardness minerals). It would still be non-scaling.
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#4: Post by DeuxInfuso »

Homeburrero provides excellent and accurate info here, as usual. In my opinion, Yes!, RO is best for espresso, with some moderate remineralization. This prevents scale formation that can cause all sorts of maintenance problems with your machine. For some reason many people think RO water is bad for you. It's basically deionized water, about like rainwater, slightly acidic (about pH=5.6).and therefore slightly "aggressive" chemically. It just needs a little alkalinity to raise and buffer the pH to 7.0 to 7.5. I add 0.1 gram potassium-bicarb per liter, or 0.38 grams per gallon, for 100 ppm TDS of non-scaling feedwater, to my KvdW Mirage; this is the Dr. Pavlis recipe. You can get a low cost reloading milligtam scale for under $30 from Hornady at Sportsman's Warehouse.

Because the effectiveness of remineralization cartridges is residence-time sensitive, the resulting amount of calcium-carbonate dissolution and pH buffering may be variable, depending on usage rate. If you use a lot of water, it may be less buffered than if you use only a little (longer residence time). It depends on the contact time, ambient temperature, nature of the marble or limestone chips & other constituents of the re-min. cartridge, and their grain size or surface area.

It is easy to keep tabs on your RO system output water, of course, just test it now and then using a low cost electrical conductivity meter (EC meter, also called a TDS meter). I use a temperature compensated EC meter (about $60 for an HM COM100), but you can use the cheaper non-temp-compensated models (many to choose from, about 15 to 25 bucks) if your water is at 25 C (77 F). Note that EC readings are very sensitive to temperature, and even with an ATC model (auto temp. compensated) the sample should be at about room temp or 65 to 80 degrees F.

For typical espresso supply water a reasonable EC target is 100 to 150 uS (micro-Siemens), for a TDS of about 60 to 100 ppm (approx. figures; actual values depend on specific anion & cation composition of your water). A reading takes just seconds and provides a quick performance check on your RO system. This provides great peace of mind, and this easily justifies meter cost.

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#5: Post by CarefreeBuzzBuzz »

Best also depends on what machine you are using. For the Flair 58 you have, what you are doing seems great. And yes change those filters at the appropriate interval. You probably are enjoying that water to drink as well, right?

We have an RO with minerals here that we use for all drinking water needs, as AZ has high chloride water. We make our own water starting with distilled for our machine with boilers. So if you ever get a boiler machine, you might want to consider that.

Why over what you have? Consistency and confidence. You don't have to worry about what stage the filters are in and thus the water is consistent and you don't have to worry about machine damage.

Enjoy your espresso.
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#6: Post by bostonbuzz »

After rebuilding some complicated espresso machines I have come to realize that nothing is more important than your water. However, there are a lot of line items on water tests. There was a thread where a guy "tested" his water and found the TDS to be acceptable, but it was causing havoc on his machine that was only a few months old - no doubt from chromium or other things he didn't test for. I know I'm not going to send out samples from an under-sink RO system to a lab for a complete analysis on a schedule and replacing filters regularly is something that can easily be forgotten, so I keep it simple and fool-proof - or put it in your work calendar.

I like distilled water with RPvalis's .1g/L potassium bicarbonate added. That way I will get no scale and no weird chemicals that may eat my boiler. Theoretically my machine will never need a rebuild again except for some old o-rings due to heat. There is whole foods with a bulk filler for .39/gal and there is a store that only dispenses distilled water within a mile from my house for .7/gal. Fill up 2 2.5g jugs and refil the one that runs out first.

Now if you own your home and are plumbed in I would spring for an oversized RO system that you can take test regularly until you an trust it and you have new filters coming in on a scheduled basis.
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