I make a two concentrates to add to distilled water. One of Magnesium bicarbonate, made by adding Magnesium Hydroxide to distilled & carbonated water, and Sodium Bicarbonate. It’s a bit variable but not hugely. I’ll get between 25-30 hardness as CaCO3 from Mg and approx 40 mg/l Alkalinity along with 10mg/l Sodium.
I wouldn’t use this in the service boiler as my aim is to not have to descale. So I manually drain and fill the service boiler every 5 weeks with distilled water, which is fine for my use and isn’t nearly as much trouble as it sounds….actually turning the machine on and off to let the pump fill the boiler would be more annoying to me.
This might not be “the best” water, but I’m personally happy with it. The taste has improved vs just remineralising with bicarbonate. Having said that, if I weren’t prepared to go through the routine with the service boiler I’d not use anything contributing hardness and just focus on alkalinity - it has a much greater impact.
I might have an attempt in the future at remineralising with a citrate salt to avoid carbonate alkalinity, but there may be other things to try too I haven’t thought of.
Also worth pointing out there are other reasons to flush the service boiler out beyond scaling. You wouldn’t want chlorides, sulfate and silica to be present in there either due to the associated corrosion risks, so whatever you do at some point you should be refreshing the water in there even if there isn’t going to be scale build up.
