Knluk
I use Magnesium bicarbonate and Sodium bicarbonate. You won’t find the former anywhere because you need to make it. I carbonate water and add Magnesium Hydroxide which reacts with the CO2 to form Magnesium Bicarbonate…..my water is about 30 GH and 45 KH.
I rate the coffee higher than with just Sodium/Potassium bicarb but I’d never advise anybody to do as I do. I remove the anti-vac valve of the service boiler every 5 weeks, syphon everything out and refill with distilled water (boilers are surgical steel). Yes, you could empty via the hot water tap but then the boiler and valve would be hot and it’s faster to just syphon it out than wait for the machine to heat up. And more cost-effective. It’s very easy for me to do it on my machine and I’m very comfortable doing that type of thing. It’s maybe a 15-minute process, if that, and the only maintenance I need to perform as my group isn’t lever actuated.
It’s worth the minor routine in my case but if somebody told me they prefered shots with just sodium or potassium bicarb compared to mine I wouldn’t be surprised. I hated shots made with the same hardness from Magnesium sulphate so ymmv.