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.

                          Verion Sounds like a plan! :-)

                          Btw, you will find an excel under @Rob1’s signature. Please take a look. It’s pretty good.

                            So my OZ turned up to today and it’s set it up and ready to go.

                            Testing with my £6.99 TDS meter from Amazon, regular tap water at room temperature reading is around 409. OZ water at room temperature is around 49.

                            That’s quite a drop of 88%.

                            I need to get the KH/GH test kit from my local aquatics supplier, but the water looks like it’s in a good place for when my Minima turns up.

                            10 months later

                            Hi all. I didn’t want to start a new thread so hoped I’d get an answer here……..I’m looking to buy an OZ, for when my Minima arrives. I understand the need to sanitise the OZ but can’t get my head around why it would need descaling (as mentioned in a this and other OZ threads) could anyone answer my (maybe stupid) question please?

                            P.S I live in a fairly soft water area.

                            Thanks

                            Al

                            • Rob1 replied to this.

                              Abcan not entirely sure….scale forms at low temperatures when water is supersaturated. Could well be it’s just to get the salts off the filters. In short, you don’t just get scale from heating the water…. though I believe the oz does that too.

                                Not sure on this one either. The filters are removed for descaling so they don’t get any treatment. If the operational filters remove scale from the water, then surely you are just descaling the route from reservoir to the filters? A short piece of tubing. Is it then that the only part of it that’s descaled is the reservoir tank and pipes to filters?

                                Edit - I suppose whatever is left after the filters starts to deposit over time especially around the heating element?

                                Not necessarily, after filtration it’s not going to heat enough to scale. Must be pipes to filters. That’s assuming the heating element only comes into contact with filtered water.