Keep the Osmio Zero water (without mineralisation)

coffeealex that’s why I was liking this thread here for a more ‘easy’ to understand for people, just want to hear what’s needed/risky in simple terms coz the detail can get so crazy with the water topic. And thanks to all who have advised here

coffeealex Well if you make water more acidic ( which is what happens when you remove all minerals) then corrosive factors come in to play.

Removing minerals will not make water more acidic; neutral pH is by definition the pH of pure water. The problem is that pure water will tend to absorb CO₂ from the atmosphere, and that can turn it into a fairly acidic liquid. Buffering it with a weakly basic compound like bicarbonates (or weakly acid - but since coffee is acidic in nature very few people enjoy adding acid to it) keeps the pH close to neutral (within relatively large bounds). “Alkalinity” (as we use it in coffee making) doesn’t necessarily equate to a high pH.

If you remove calcium and magnesium compounds, or (bi)carbonate ions, scale won’t form. The problem is that Ca and Mg make coffee taste better to a large proportion of people, and bicarbonates are an easy method to raise alkalinity (which also makes coffee taste better, in addition to some anti-corrosion effect… which BTW isn’t always present, depending on temperatures and pressures).

It’s not necessarily complicated, but there are a lot of factors interplaying, and many are personal choices. In addition to the matter of “coffee taste”, there are significantly different opinions on what is a safe or acceptable amount of “corrosive” compounds (chlorides, sulphates, etc.), or a tolerable amount of/time to (de)scaling.

CoyoteOldMan Thanks for clarifying that technical aspect re acidity. Is the fact that pure standing water is absorbing carbon dioxide the reason you often hear people say to only use water on demand as needed rather than leave large amounts in the espresso water tank? Also is there a simple formula to work out how much bicarbonate of soda to add if using pure water to bring the ph neutral or thereabouts? How do you measure very small amounts of bicarbonate of soda as I would assume you are talking about less than a gram a time?

coffeealex the reason you often hear people say to only use water on demand as needed rather than leave large amounts in the espresso water tank?

I think the reason people are worried about that is more to with biological contamination. RO/DI water does not contain chlorine, which tap water does…

coffeealex Also is there a simple formula to work out how much bicarbonate of soda to add if using pure water to bring the ph neutral or thereabouts?

A buffer is not a neutralising agent. https://en.wikipedia.org/wiki/Buffer_solution

coffeealex How do you measure very small amounts of bicarbonate of soda as I would assume you are talking about less than a gram a time?

Indeed. Which is why many people (me included) use concentrate saline solution. I, for example, use 1.60 grams of KHCO₃ to 400 ml of water to make my concentrate, and then use 20 ml of this solution in 980 grams/ml of pure water, which gets me 80 mg/l of bicarbonate (equivalent to a KH of 40 mg/l of CaCO₃). Otherwise, buy a mg resolution scale (they are cheap nowadays), and spend a bit of time with a pair of tweezers every time you need to mix a litre…

CoyoteOldMan - 🤣🤣🤣🤣🤣

I’ll just leave this here:

Been there, done that. The concentrate route is sooooo much easier! 🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣

coffeealex It seems like you’re confusing terms alkalinity and alkaline. Alkalinity refers to buffering capacity or ability to neutralise acids and maintain a stable pH. Pure water will have a neutral pH of 7. As already covered, how much bicarb to add depends on the alkalinity you want and the amount of water you are treating.

CoyoteOldMan I, for example, use 1.60 grams of KHCO3 to 400 ml of water to make my concentrate, and then use 20 ml of this solution in 980 grams/ml of pure water, which gets me 80 mg/l of bicarbonate (equivalent to a KH of 40 mg/l of CaCO3).

Could i do the same mix on pure RO water? Does the saline solution Keep?

Rob1 You are right I was confusing the two. still on my journey of learning.

coffeealex - adding 80mg/L of sodium bicarbonate works. This will prevent corrosion, as NaHCO3 will act as a buffer. In addition, it won’t scale, as it does not contain magnesium or calcium in its formula.

And yes, you still need to refresh your service boiler periodically, by drawing a mug of water weekly and/or a full refresh every 6 weeks or so, check TDS to keep tabs on it. Like any dissolved solids, it will be left behind in the boiler as you draw steam out, which is pure (distilled) water.

CoyoteOldMan The saline solution keeps fine in a closed bottle in the fridge (1 month +) - nothing to spoil

I keep my concentrate in a cool, dark place, but not the fridge. There’s no smell or anything after two months. I however use distilled water so any organic form is boiled to death anyway.

MediumRoastSteam Thank you, makes total sense

coffeealex “Mineral content” (TDS or dry residue) and “probability of scaling” are not the same thing. You could add a lot of sugar to water (more than the weight of water!), and it wouldn’t scale at 130 °C. Heck, you could add quite a lot of copper sulphate, and it wouldn’t scale.

For scale to form you need Ca and/or Mg and (bi)carbonate (or sulphate, but far less likely) ions in solution. If you only add bicarbonate of sodium or potassium, there is no Ca or Mg, so scale will not form.

Flushing is still required as at some point, as bicarbonate salts convert to carbonate with heating, and carbonate solutions can be corrosive. Do you need to flush frequently? No, probably once every few months - and that’s largely out of caution.

Personally I think as far as Oz is concerned, they should have gone the way of Skuma, by having a choice of mineralised/demineralised water by just pressing a button and not having to use an empty cartridge. Surely a simple bypass of the cartridge in the piping would give that choice. Then if you wanted mineralised water you press one button or demineralised you press another or hold the same for longer.

Or have a two cartridge system. One exclusively for espresso machines by not using magnesium or calcium carbonate and another with the minerals for taste. The best of both worlds

My Minima is turning up next week and I’m thinking of getting the Osmio Zero to use in the brew and service boilers.

Am I right in thinking that with the Osmio Zero will purify and remineralise my tap water with no other intervention needed, I shouldn’t get any scale?

@LMSC Eiffel Good tips.

I have no problem in drawing a cup from the service boiler after steaming milk and monthly flushing.

Planet Organic have a good deal on, so I think I’ll make the jump.

@Eiffel How are you testing your TDS?