oksako wrote:Reading through other threads always leads me to the question, why so often brita filters and in tank filters are recommended, while rpavlis water seems to be the allrounder/no brainer solution?

You can use a Brita to remove chlorine/chloramine, and follow that with an in-tank conventional softener to remove hardness which can be a good solution for most water, provided you take care to replace the softener as needed. That approach will not, however, do anything to remove chloride ion. Rpavlis is the allrounder solution because it guarantees good alkalinity, no scale, no chlorine/chloramine, and no corrosive chloride ion.

tennisman03110 wrote:A Brita won't soften water.

Most Brita filters contain WAC resins that do tend to decarbonize and soften water, but should not be relied on for softening. In the US and Canada you can get Brita 'longlast' filters that do not contain these resins and leave your hardness and alkalinity unchanged. To my mind you are better off using the longlast for chlorine/chloramine removal if you are using some sort of true softening filter in the tank.

homeburrero wrote:Right. At room temp and in equilibrium with air it has a pH of around 8.2 and an alkalinity (acid buffering capacity) of 50 mg/L as CaCO3. The half-strength recipe would have a pH of around 7.9 and an alkalinity of 25 mg/L as CaCO3.

Thank you very much again.

Finally, my Lelit Elizabeth arrived, that's the one I have chosen. I also have already bought 20l (4 x 5l) of distilled water, picked up my potassium bicarbonate from the pharmacy and thus I am ready to start! So to be absolute sure with everything, just a couple more short questions:

1. I have a very cheap china scale (https://www.amazon.de/-/en/Foraco-Pocke ... Z9YPX?th=1) and I am wondering whether it is more "secure" to put 500mg / 0.5g of KHCO3 into the 5l container or to create a concentrate, like 5g KHCO3 into 1l distilled water to get a concentrate and 100ml of that concentrate into 5l container yielding 100mg KHCO3 per liter? Do you think such a cheap scale is "precise" enough? I testet the scane with a 1 cent coin which should weight 2,3 grams and the cheap scale actually showed 2.29g, so exactly what i would expect. However I can't verify if it can accurately measure 0.5g, because I don't have an item where its weight is standardized to 0.5g.. Any advice?
2. Considering http://www.aqion.onl/ I would get a pH of 8.27 when my water has 100mg KHCO3 per liter (and also the safety data sheet of the potassium bicarbonate says ph between 8.0 - 8.6 with 50mg/l). I found it kind of interesting, that this little amount of KHCO3 will raise the ph from approx. 5 to 8.2 (regarding the internet the ph of distilled is supposed to be around 5). So this is actually not a question, just something I found really interesting. So little and its no longer acidic but neutral.
3. Do you think I should buy a ph test strip to test the distilled water before and after I mix in the KHCO3? Is it smart to do so, if yes, why?
4. A little bit of topic: Is Puly Caff acidic? I assume not, right? And that's why I can use it without any concerns with my machine even if it has brass group head etc.
5. Do you recommend anything else to start with my journey? What is you experience with when to change from the simple rpavlis to something else? Never?
6. EDIT: One more question: Just out of curiosity, how can I convert 100mg/l of KHCO3 (potassium bicarbonate) to HCO3- (hydrogencarbonat)? I want to understand how "hard" my water will get with rpavlis.

I am as always really looking forward to your responses.

Stay happy, best whishes!

oksako wrote:1. I have a very cheap china scale (https://www.amazon.de/-/en/Foraco-Pocke ... Z9YPX?th=1) and I am wondering whether it is more "secure" to put 500mg / 0.5g of KHCO3 into the 5l container or to create a concentrate, like 5g KHCO3 into 1l distilled water to get a concentrate and 100ml of that concentrate into 5l container yielding 100mg KHCO3 per liter? Do you think such a cheap scale is "precise" enough? I testet the scane with a 1 cent coin which should weight 2,3 grams and the cheap scale actually showed 2.29g, so exactly what i would expect. However I can't verify if it can accurately measure 0.5g, because I don't have an item where its weight is standardized to 0.5g.. Any advice?

High precision is not at all necessary here. If you want .5g in 5 liters and your scale gives you .3g or .7g, you are still fine. But most of us find it much more convenient to use a concentrate rather than try to measure and add such small amounts.

oksako wrote:2. Considering http://www.aqion.onl/ I would get a pH of 8.27 when my water has 100mg KHCO3 per liter (and also the safety data sheet of the potassium bicarbonate says ph between 8.0 - 8.6 with 50mg/l). I found it kind of interesting, that this little amount of KHCO3 will raise the ph from approx. 5 to 8.2 (regarding the internet the ph of distilled is supposed to be around 5). So this is actually not a question, just something I found really interesting. So little and its no longer acidic but neutral.

Yes, the pH of distilled can vary widely based on the amount of dissolved CO2 in the water, and a tiny amount of bicarbonate buffer raises it above neutral and makes it much more predictable.

oksako wrote:3. Do you think I should buy a ph test strip to test the distilled water before and after I mix in the KHCO3? Is it smart to do so, if yes, why?

I don't, I never bother measuring pH. An alkalinity drop test is better, and for a quick sanity check you can use an inexpensive TDS meter. A simple TDS meter with the 0.5 calibration factor will read about 60 ppm on 25C water with 100 mg/L KHCO3.

oksako wrote:4. A little bit of topic: Is Puly Caff acidic? I assume not, right? And that's why I can use it without any concerns with my machine even if it has brass group head etc.

It's a very basic (high pH, sodium carbonate) detergent, should be no problem used as directed.

oksako wrote:5. Do you recommend anything else to start with my journey? What is you experience with when to change from the simple rpavlis to something else? Never?

No, but compared to most people I'm somewhat of a non-believer in the importance of water tweaking for good coffee taste. My own home recipe has some hardness minerals, but I'm not convinced it's any better than simple rpavlis.

oksako wrote:6. EDIT: One more question: Just out of curiosity, how can I convert 100mg/l of KHCO3 (potassium bicarbonate) to HCO3- (hydrogencarbonat)? I want to understand how "hard" my water will get with rpavlis.

KHCO3 has a molar mass of 100 g/mol, and HCO3- has a molar mass of 61 g/mol. So 100 mg/L of KHCO3 (1 mmol/L) has 61 mg/L of HCO3- ion. And the hardness (GH) is zero, the alkalinity (KH) in CaCO3 equivalents is 50 ppm CaCO3.