coffeealex Yep. All correct. 80 mg/l KHCO3 will get you 40 KH and 120 mg/l will get you 60 KH. 100 mg/l is 50 KH. All are fine.

“my” concentrate is 1.60 grams of KHCO3 in 400 ml water, then use 20 g (or ml) of this per litre of water to get 40 KH. The 400 ml is because I had a jar with a screw top that would hold that much, so scale it for whatever you are going to use - don’t make too much of it, or you’ll need months to use it (and probably end up throwing some away).

If you want to stick to 100 mg/l (50 KH), then use 2.00 grams in 400 ml of water, then use 20 g (ml) of concentrate per litre.

      CoyoteOldMan Thank you for this. I know that you have to periodically flush the service boiler to prevent a build up of minerals. What would happen if you never flushed it? Would it increase the scalability?

          coffeealex If the only thing you are adding to the water is bicarbonate, scale will never be an issue. However, at some point, corrosion may be… as bicarbonate turns to much more alkaline carbonate. And at some other point the (bi)carbonate will saturate the water and start precipitating, which can cause all sorts of problems from clogging to disgusting-tasting coffee.

            Thanks. This is the bit that always confuses me : I understand the scaling bit but still not fully understanding the corrosion part. I thought water was more corrosive the more acidic it became? Is there then also a point at which it is more corrosive when alkaline levels increase by quite s bit due to the accumulation of those in the boiler? Sorry for coming across a bit ignorant in all this.

              coffeealex Alkaline substances can be highly corrosive. “Caustic soda” (sodium hydroxide) is not called ‘caustic’ by chance.

              Corrosion of metals by alkaline substances is usually less of a problem than by acids, but it’s not absent. 316/316L steels perform very well against alkali corrosion, but 304 steel and copper less so (copper particularly in the presence of carbonates).

                  coffeealex Corrosion is not just driven by pH, but also by salts concentration (TDS), and which salt type(s), and the metal(s) involved, and their surface finish, and their physical layout, and, and, and… I’d rather use a rule of thumb and say that if you are using only bicarbonate, flushing water out and replacing it every couple of months is more than enough (unless you are in a commercial/high volume environment). You could probably go six months without any issues.

                    Many thanks for the concentrate idea, discovered my scales really aren’t that accurate measuring 0.1 gm though I thought later they might do better if I had put a weight on rather than starting at 0. As the new mix works its way through be interesting to see if the taste reverts, the oddest thing is that with zero water coffee tastes dry.

                    I have noticed that hardness in water is measures in multiple ways: ppl, mgl, french degrees, german degrees, caco3 etc. Which do most people use?

                      coffeealex ppm and mg/l are pretty much the same (density of water is not 1.000 at room temperature, but close enough at 0.997). My observation is that ppm in CaCO3 equivalents is the most widespread measurement in coffee circles, so that’s what I use.

                      BTW - A chemist would want to use mol/l or mmol/l, which - if expressed in CaCO3 equivalents - have an almost exact (if coincidental) factor of 100 to ppm.

                      French degrees are the same as ppm, with an exact factor of 10 in the middle, which means the “outliers” are the Imperial/USC-based units (degrees Clarke and grains/gallon) and the “German” unit (dGH/°dH - using CaO instead of CaCO3).

                          coffeealex There isn’t one, as solubility of CaCO3 (and MgCO3) varies quite significantly with temperature, and hardness in CaCO3 equivalents coming from different ions is not necessarily ‘equivalent’ from a scale formation point of view.

                          Rob1’s spreadsheet implements a calculation for a ‘maximum allowed hardness’ at a given temperature derived from an empirical formula which gives you a reasonable idea under certain assumptions (i.e. that the alkalinity in the water comes from bicarbonate ions); that could be incorrect if - for example - one were to use calcium citrate and no (bi)carbonates to get an alkaline buffer.

                              I’m starting to think I’m not bright enough to own a coffee machine and perhaps I should just get my Sage out of the loft which ran on hard tap water for 5 years without issue. Reading that Sodium Bicarbonate was easy to find in a supermarket I picked up a likely tub in Waitrose as it had Bicarbonate of Soda on it which sounded similar but I suspect isn’t the right stuff at all, I must say I have amazing bubbly crema now and it’s definitely tasting better than zero water. Thoroughly confused as Wikipedia suggests my tub of sodium hydrogen carbonate is Sodium Bicarbonate. My last chemistry lesson was in 1968. Help.

                                SurreyAlan

                                Bicarbonate of soda

                                Baking Soda

                                Sodium bicarbonate

                                NaHCO3

                                Sodium Hydrogen Carbonate

                                They are all the same thing.

                                Just make sure you don’t confuse yourself between Baking Powder and Baking Soda, as You definitely don’t want Baking Powder into you coffee. 👍

                                  SurreyAlan it had Bicarbonate of Soda on it which sounded similar but I suspect isn’t the right stuff at all, I must say I have amazing bubbly crema now and it’s definitely tasting better than zero water

                                  How much did you use?

                                      CoyoteOldMan

                                      Thanks again. I thought it probably wasn’t a straightforward answer. In any case I am going to stick to your formula to keep things simple, otherwise my kitchen will as start to feel more like a chemistry lab.

                                      Just one other curiosity. Whats your views on using osmio zero with the remineralisation cartridge left in, as opposed to a blank one. I appreciate it is reintroducing minerals back in, but do you feel it would as a result ( in general) lead to the likelihood of scaling?

                                      • Rob1 replied to this.

                                          MediumRoastSteam A little bit of hyperbole there, after packing in chem, physics and biology I carried on with the easy stuff like English and RK, back then so long as you had Maths and English no one cared much what the others were. It was a rough 0.2 gm in 2l which gave me a TDS of 73 which was only a little less than Tesco Ashbeck. What’s coming out of the group is 53 yet it’s astonishing how different it tastes and feels in the mouth. Going forward I’ll make up a rather more accurate concentrate. I have a lot of washing soda under the sink which I’ll definitely not be using.

                                              SurreyAlan I am no expert here as others are much better informed than me. TDS as far as I know is not an indicator of scaling potential ( if that is what you are trying to achieve) as it only tells you what total minerals there are but does not identify which ones they are.

                                                  Indeed, but with a TDS of 0 from the zero jug the taste wasn’t there and the drink just felt dry whereas with something added it tastes again and is wet. Quite astonishing how such a tiny amount makes such a difference.

                                                    coffeealex - the exception here coffeealex is that SurreyAlan is using Zero Water (presumably 0 TDS, or very near it) and sodium bicarbonate. Therefore it’s safe to say all the dissolved solids are from sodium bicarbonate (the only salt added) which does not scale.