Thanks Rob1 !
I might be wrong, but I understand that with the Lelit Elizabeth I cannot independently flush the steam or brew boilers. To flush, you run the hot water wand until it stops running. What you end up with (in your measuring cup or beaker) is the full contents of the brew boiler, followed by the contents of the steam boiler.
Both are served by the same water supply. So if I purge using ZeroWater or distilled water, I end up with that new water in both the brew and steam boilers, which would then not be the water that I want to permanently have in my boilers or brew with. So I would then have to purge a second time with my actual water recipe (inclusive of the potassium bicarb and the magnesium hydroxide).
All good. If I end up liking adding the magnesium and it is better/safer to initially purge with soft water, such as ZeroWater, and then repurge with my water recipe (bicarb and magnesium) then I will just do that.
So question: do I need to do the above described double (twice) purge, to avoid scale.