No salt. Avoid chloride. If you want sodium but want to keep it at scaa recommended 10mg/l use both Potassium and Sodium bicarb to get your alkalinity to 40mg/l - you can go higher or lower with alkalinity if you want but 40 is a good start. No need for hardness, but if you really want to try it and think it makes enough of a different to complicate maintenance do what you want…you have a robot to test on to make it easier. Magnesium isn’t any better than Calcium for scaling.

    dutchy101 If you aren’t getting smells or colours in the stored water, it’s probably OK. The only way to know is to do a microbiological exam, as presence of bacteria/algae/protists would be the issue. I don’t think “3 days” is a hard limit…

        Rob1 hi Rob, good to have your input. As mentioned above, I am hopeless for chemistry. But would love to hear your water recipe? I will try on my Robot but the main goal is optimzing the performance and minimising scaling on a boiler machine.

        • Rob1 replied to this.

            CoyoteOldMan

            I’ve been doing this now since February and haven’t died yet, so hopefully all is OK. I have a Skuma RO unit coming in October, when I will be changing how I do things.

              Every time a water discussion comes up on here, I feel like I go straight back to square 1 in terms of my understanding of things - lol. Perhaps I might shift to a system of only making up just 1 × 5 litre batch of water at a time until the Skuma arrives as opposed to the 2 × 5I have been making over the last 6 months.

              The water is certainly not discolouring, nor does it smell so hopefully it has all been OK so far.

              @Cuprajake - how long do you tend to make up and use your concentrate for?

                PROB LONGER THAN I SHOULD LOL

                Decent De1pro v1.45 - Niche Duo - Niche Zero - Decent is the best machine ever made -

                i make a 400ml concentrate, then i make up 8l of ro water at a time, this is stored under the sink in the dark, usually about 2 weeks is for use

                Decent De1pro v1.45 - Niche Duo - Niche Zero - Decent is the best machine ever made -

                dutchy101 FWIW, I make 400 ml of concentrate, kept in the fridge in a screw-top jar (ex ice-cream jar). It lasts me ~1 month.

                    Thanks. In terms of an immediate change, I think I’m going to move down to making just one 5l batch using the Zero water at a time until the RO unit arrives. I might move to a concentrate at that stage.

                    I probably also need to find some better bottles for storing water than re-using old Ashbeck bottles.

                      CoyoteOldMan still thinking how I should approach this best.

                      Mind sharing how much mg of potassium bicarbonate did you put in the 400ml concentrate? And how much (X)ml of concentrate do you put in (Y)ml of purified water? Appreciate that.

                          Honestly - Keep it simple like this @Knluk :

                          • In 500g (or 500ml) of distilled or RO water, add 5g of sodium bicarbonate, or 5g of potassium bicarbonate. Put that in a bottle, store it. This is bottle “C” - C is for Concentrate.
                          • Put 1 litre of distilled or RO water into a bottle. This is bottle “B” - “B” is for Boiler safe water;
                          • Using a syringe draw 10ml from bottle “C”; (You can also try 8ml, see what works for you)
                          • Empty the contents of the syringe into bottle “B”.
                          • Empty the contents of bottle “B” into your coffee machine tank.
                          • Chop chop, bob’s your uncle, all set.

                            Knluk - It’s like riding a bike: You’ll do it with your eyes close and you’ll never forget! 🤣

                              Knluk I think following the instructions that MediumRoastSteam provided above you can’t go wrong. For completeness, my concentrate uses 1.60 grams of KHCO3, and I use 20 ml/grams of concentrate per litre/kg of water (theoretically 20/980, but I’m often not that precise!).

                                    dutchy101 We have two ‘posh’ bottles of Voss water used to store drinking water in the fridge, bought pretty much purely because of the bottle! 😁