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  • #31
    Re: RO water bad for coffee machines?

    Originally posted by Bill link=1209725970/15#23 date=1209866233
    Originally posted by Sparky link=1209725970/15#21 date=1209855799
    This is the reaction that takes place with aluminium and water to produce hydrogen (in the presence of NaOH, which dissolves the native oxide). So in the context of a coffee machine, if the machine is new with clean fresh surfaces and RO water is continually cycled through the machine, native surface oxides will be dissolved and the bare metal may be oxidised by reducing the water.
    But there is no NaOH present in RO water, so therefore the native oxide wont dissolve??? (Im not saying it wont, Im just asking the question)

    And brass and stainless steel (the materials that most espresso machines are made from) are much less susceptible to corrosion than aluminum.

    Bill
    The lack of ions in pure water will cause the native oxide to dissolve even with a vanishing (but not zero) solubility. Dissolved oxygen and CO2 may help both the removal of native oxide and the oxidation process. In a boiler there should be much less dissolved gas, but the high temperature will increase solubilities and speed up chemical reactions.

    In short the chemistry of water is very complex. Take away the ions and many things that are virtually insoluble will dissolve. There is a lot of zinc in brass, which is a very electro-active metal, so expect brass to be more strongly affected.

    The aluminium example was meant just to point out that metal can react with water. The aluminium reaction is vigorous, but zinc will behave similarly and copper less so. The only thing protecting the metal surface is a native oxide. Once this is removed (by dissolving in water with low ion content) the metal can corrode. Continual use of ion-less water will continue this process by replacing the water and preventing ion biuld-up.

    That said, Im not sure just how ion-less commonly available RO water is. At work we can achieve a resistivity of 18.2 MOhm-cm. I doubt that home systems or RO drinking water is close to that grade. Ive been using Pureau RO water in my machine with no problems so far. However I often use filtered water as well and the residual ions in the boiler should keep things fine. Certainly there is no metallic smell to the steam, so I doubt there is any adverse water chemistry occurring. This water may only be from a single pass RO system, not the ultrapure water that a high end Millipore laboratory system produces.

    The bottom line is that the manufacturers dont recommend it and no cafe uses it. Therefore youre not gaining anything by using it, but may in fact be losing something, be it taste or a slowly dissolving machine.

    At least this thread has raised some awareness.

    Cheers,

    Mark.

    Comment


    • #32
      Re: RO water bad for coffee machines?

      Originally posted by Sparky link=1209725970/30#30 date=1209878465
      That said, Im not sure just how ion-less commonly available RO water is.
      Yes, thats another point. Quote from "Jim Schulmans Insanely Long Water FAQ"


      RO should produce virtually pure water (below 1 mg/l total solids); however, mineral removal is compromised when the amount of waste water is reduced. For instance, supermarket RO vendomats in very hard water areas may put out as much as 50 mg/l hardness and alkalinity levels.

      Comment


      • #33
        Re: RO water bad for coffee machines?

        Well, its certainly interesting, and it might be best for me to use an ion exchange system as JavaB mentions, but Im still not sure of the optimal mineral level to both avoid corrosion AND scale.

        To reiterate, I dont drink the stuff, as its an HX machine, as many other CSs will also have. The water I drink is tap water, and is already fairly soft, according to the published figures. So health is not the issue (although I agree completely with the comments about absurd over-purification of everything). All Im worried about is the life of the boiler. Thanks for the link to Jim Schulmans page. Ironically, it was Jim who first suggested using RO water in the boiler (same Elektra as mine).

        Mark,
        Since you also seem to use Pureau, youve actually made me wonder if just using tap water to refill the boiler every now and then in place of the RO (i.e. alternating tap and RO) might introduce enough ions to prevent corrosion, while still avoiding scale. Its hard to say how often the total volume of 1.8 litres is turned over, but probably once every three weeks or so. To be honest, I would really rather not be bothered with the Pureau if I thought the boiler would be o.k.

        matt

        Comment


        • #34
          Re: RO water bad for coffee machines?

          Very interesting reading AM,

          Always new there was a good reason to avoid this stuff, quite apart from it tasting pretty awful and making terrible coffee.....  

          Thanks mate ,
          Mal.


          Unless one is drinking black coffee I do not agree that RO or Distilled water would affect the taste. Milk coffee drinkers would not be able to discern whether the 30mil shot in their cuppachino etc was made from whichever water.

          I think there is more important things distorting the taste of coffee, mainly that yucky plasticky taste from using milk in plastic bottles. For that reason I refuse to use anything but cartons. Most times you can get a whiff the plastic odour by placing your nose near bottle mouth.

          Comment


          • #35
            Re: RO water bad for coffee machines?

            Originally posted by cremakid link=1209725970/30#33 date=1209899109
            Very interesting reading AM,

            Always new there was a good reason to avoid this stuff, quite apart from it tasting pretty awful and making terrible coffee.....  

            Thanks mate ,
            Mal.


            Unless one is drinking black coffee I do not agree that RO or Distilled water would affect the taste. Milk coffee drinkers would not be able to discern whether the 30mil shot in their cuppachino etc was made from whichever water.

            I think there is more important things distorting the taste of coffee, mainly that yucky plasticky taste from using milk in plastic bottles. For that reason I refuse to use anything but cartons. Most times you can get a whiff the plastic odour by placing your nose near bottle mouth.
            Yes and no I suspect. SOme may have a more discriminatory palate, some might not.

            With training, many people can pick up things they had never noticed.

            Nevertheless, the is no need whatsoever for RO in espresso machines unless its remineralised...

            Chris

            Comment


            • #36
              Re: RO water bad for coffee machines?

              ck dont make generalisations by assuming all milk coffee drinkers cant taste any difference.
              There are people out there with vastly superior palates to mine; its more than likely they can tell the difference.

              This whiff of plastic odour of which you speak; is it there when you open the bottle for the first time?

              Comment


              • #37
                Re: RO water bad for coffee machines?

                Originally posted by Dolcimelo link=1209725970/30#32 date=1209895446

                Mark,
                Since you also seem to use Pureau, youve actually made me wonder if just using tap water to refill the boiler every now and then in place of the RO (i.e. alternating tap and RO) might introduce enough ions to prevent corrosion, while still avoiding scale. Its hard to say how often the total volume of 1.8 litres is turned over, but probably once every three weeks or so. To be honest, I would really rather not be bothered with the Pureau if I thought the boiler would be o.k.

                matt
                Why not just use a Brita jug. Thats what Im currently using. It has an ion exchange resin that will remove some of the calcium and magnesium ions and replace them with soluble sodium ions. After say a month of filter water, Ill go back to RO water for a few weeks to descale the innards a bit and so on... Ive never gotten to the point where my level sensor didnt work, so theres plenty of ions about, even after a month or so of RO water. Another option is say a 50/50 fill of Brita filtered with RO. At least for peace of mind, its probably best to steer clear of a diet of pure RO.

                Cheers,

                Mark.

                Comment


                • #38
                  Re: RO water bad for coffee machines?

                  Thanks Mark, I guess thats the easiest way. I just thought it would be even easier if I mixed it with tap water, but had no idea what level of ions I would end up with. I wish there was a way of easily testing closed HX boiler water - but I wish there was also a way of knowing just what the optimal level of mineralisation was for avoiding corrosion and scaling.

                  matt

                  Comment


                  • #39
                    Re: RO water bad for coffee machines?

                    matt,

                    My machine had done 18 years of "hard labour" in the Cafe here in Perth before I bought it..... fed through the same water softener I am now using..... off the local Perth ultra hard water.

                    The softener was religiously recharged every month..... and was subject to very high usage.... (I recharge every 2 months which is probably more often than required!)

                    When I got the machine I did a strip and descale...... and whilst there was some scale on the boiler walls it was pretty good for 18 years of heavy usage. The element was pretty clean as well. IMHO it could have done many more years service and the scale still wouldnt have been a problem.

                    Comment


                    • #40
                      Re: RO water bad for coffee machines?

                      Actually, something Ive just thought of. In a HX boiler, the only way the water level decreases is through steam evacuation. Therefore, any mineral ions dissolving in the water would become more concentrated over time, would they not? Would this mean that they will get to a certain concentration and then stop taking more from the boiler surfaces, or does something keep the process going? Even if I top up with RO water, will those ions still be present in solution? Moreover, if I add some mineralised tap water, will those ions also remain in the boiler?

                      Is this what will happen, do you think? Remember, this is a closed HX boiler, with no liquid water drawn from it.

                      matt

                      Comment


                      • #41
                        Re: RO water bad for coffee machines?

                        Thanks JavaB, Im convinced that what you and Mark say is correct. Still, pretty interesting problem that certainly had not occurred to me.

                        matt

                        Comment


                        • #42
                          Re: RO water bad for coffee machines?

                          Originally posted by Dolcimelo link=1209725970/30#39 date=1209903589

                          Is this what will happen, do you think? Remember, this is a closed HX boiler, with no liquid water drawn from it.

                          matt
                          matt,

                          So you use the boiler for texturing milk? If so the autofill will suck whatever water is in the reservoir into the boiler to replace that which has left as steam...... so if you have "normal" water in the reservoir that will get sucked into the boiler.

                          Yes, in theory only steam (pure water) leaves but in practise a small amount of salts etc can also escape. The ion levels would remain substantially constant if you topped up with RO water...... but I honestly cant see the need to chop and change between the type of water you use..... just use softened water for the machine - and all will be fine. Id also draw water off every so often..... just so the water in the boiler is relatively fresh.

                          Comment


                          • #43
                            Re: RO water bad for coffee machines?

                            Hi JavaB,

                            There is no autofill. When I want to add water to the boiler I press a button to manually fill it. It does come from the reservoir, but I simply drain this (and the line to the pump) and replace it with the RO to fill the boiler (a small amount of water every few days). The water level drops solely from using the steam. If I dont texture any milk, the boiler will keep its level. However, since my partner and I drink one or two cafe latte each for breakfast, the boiler water does eventually get replaced.

                            I will change to softened water from now on.

                            matt

                            Comment


                            • #44
                              Re: RO water bad for coffee machines?

                              Originally posted by Dolcimelo link=1209725970/30#42 date=1209905332
                              Hi JavaB,

                              There is no autofill. When I want to add water to the boiler I press a button to manually fill it. It does come from the reservoir, but I simply drain this (and the line to the pump) and replace it with the RO to fill the boiler (a small amount of water every few days). The water level drops solely from using the steam. If I dont texture any milk, the boiler will keep its level. However, since my partner and I drink one or two cafe latte each for breakfast, the boiler water does eventually get replaced.

                              I will change to softened water from now on.

                              matt
                              With an HX boiler, if you keep filling up with mineralised water (and with essentially only distilled water leaving through the steam arm), the minerals will naturally increase in concentration over time which will eventually cause scaling no mater how little minerals were present to start with. This is one of the reasons why you need to periodically flush some water from the boiler (via the hot water tap for example) and top up with low mineral water (or fresh, softened tap water), thereby lowering the concentrated minerals back down to a non-scaling level.

                              Im in the same situation as you. My machine is also an HX with manual boiler fill. What Ive been doing is top up the boiler through the week with the reservoir water (which is filtered tap water running through the softener cartridge in the reservoir) and periodically (once every week or two) empty a portion of the boiler water out the hot water tap, and top back up with Pureau to prevent the mineral content getting too high.

                              Water hardness can be measured with testing strips, or you can use a TDS meter to measure mineral content. (note that these 2 testing procedures dont measure exactly the same thing)


                              regards,
                              Bill

                              Comment


                              • #45
                                Re: RO water bad for coffee machines?

                                Thanks Bill. If I had a hot water tap it would be very simple indeed. However, I dont, so the only way to empty the boiler is to open the steam arm and physically tip the whole unit on its side to let the water run out. Not actually as hard as it sounds, since its not really that heavy. However, also not something Id like to do every week - or even two. Thats why I was thinking of just sometimes using tap water from the reservoir to mix with the Pureau. Maybe I could then get away with emptying it once a month, or something. I wish I knew just how much mineralisation it could sustain without problems, then I would test it to see how the concentration changed over time, which would then give me an idea of the best procedure. Whod have thought it would be so complicated?

                                BTW, where would I procure some testing strips? And would that suffice, do you think?

                                Thanks,
                                matt

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