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

                      No (theoretical) difference. Some people find a difference in flavour between demineralised water through RO, de-ionisation or distillation.

                      The saline solution keeps fine in a closed bottle in the fridge (1 month +) - nothing to spoil… and difficult for algae/bacteria/fungi/protists that accidentally fall into it to multiply in the cold and dark without nutrients.

                          CoyoteOldMan In trying to keep this simple would this scenario work : Lets assume I have a starting point of 0 tds ( I have removed all minerals etc say with zero water) At this point i have scaling under control but corrosion/ taste could be a problem. So I add bicarbonate of soda at 80mg per litre. Now I have both scaling and corrosion in check as I have added an alkalinity buffer to stop the ph becoming too acidic. Surely this would work? At this point is flushing of the service boiler still required as mineral content is very low meaning scaling is unlikely?

                              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.

                                    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.

                                      17 days later

                                      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

                                      16 days later

                                      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?

                                        Based on my experience with the Evo Leva (same boilers as the Minima), I’d suggest the simple additional step of drawing around a cup of hot water from the service boiler after steaming milk when using the Osmio Zero and the remineralisation cartridge.

                                        I’ve done so for over a year and the TDS of the hot water (after letting it cool down) stays stable at about 55 ppm… and thus I haven’t felt the need for a monthly full flush but YMMV

                                          @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?

                                            I have a cheapo “TDS-3” meter bought from less than £4 on Amazon.

                                            While I don’t know how accurate it is, I get distinct but consistent reading over time when measuring tap water (upper 200 ppm), water straight from the Osmio (30-40 ppm) and from the service boiler (~55 ppm).

                                              Eiffel I think I need to get one in the next Amazon Prime Day sale and see where I’m at before and after with my tap water.

                                              I’m in NW London (Affinity Water) and PPM looks to be around 352. Hopefully I can get this down somewhat with the OZ.

                                                Also, get a drop kit, measure the GH and KH of your water from the boiler at room temperature. Test on a sample of 20 ml or 40 ml for each test, multiple 17.9 by number of drops and divide the output by 4 (if 20 ml) or 8 (if 40 ml). You can do it on your monthly full flush.

                                                  LMSC Absolute star!

                                                  Going to make an excel spreadsheet so I can see month by month what my GH and KH is.

                                                  • LMSC replied to this.