Knluk KHCO3 (potassium bicarbonate) - 80 mg/l - for avoid scaling and if use sodium bicarbonate can also enhance taste?
The purpose of potassium (or sodium) bicarbonate is not to “avoid scaling”. Water for brewing coffee needs some alkalinity to taste good (and some alkaline buffer will also help with corrosion - pure water can become acidic by absorbing CO2 from air). However, potassium or sodium bicarbonate by itself will not create scale.
Knluk the Magnesium can help avoiding scaling
Quite the opposite, unfortunately. Magnesium and calcium salts are likely to cause scale. Magnesium (carbonate) is more benign than calcium - partly because it doesn’t tend to ‘stick to itself’ as much as calcium carbonate does, and partly because it creates less amount of scale to start with. However, water containing (bi)carbonate ions and calcium or magnesium ions in quantities generally believed to be ‘good’ for making coffee will scale.
Knluk Does steam boiler has a scaling point? How can I check the point? Reload with pure water? Does it need to be mineralised pure water?
Dissolved minerals in a steam/service boiler will tend to get more concentrated over time, as steam is extracted but none of the minerals/salts in the water. If you use the spreadsheet that @Rob1 has created, it has a page to help you predict ‘when’ it will scale, depending on your water characteristics and usage, but the TL;DR message is “it will scale if you use calcium and/or magnesium”.
It is a good practice to dilute the minerals by discharging some mineral-rich water regularly (every day) and replacing it with (at least) brewing water. Even better is to empty the boiler regularly, and re-fill it with de-mineralised water.
