LMSC I understand some water lost in steaming as it leaves the minerals as deposit. In my Evo, for example, I steam 350g of milk once a day. After steaming for about 35s, the pump has never kicked in, during the last 6 months, unless I open the hot water tap.
I would find that really strange (unless you open the hot water tap every day or two). Maybe the evo just has a long refill and a deeper probe tip. On the Minima when I steam for about 15 seconds I’ll get a refill either the next morning when the machine turns on via timer or when I use steam again and the boilers cool down. Almost always get a refill when the boilers cool down/when the machine comes on first thing if turned off when still warm after steaming a larger quantity e.g 40 seconds of steaming.
The amount lost is small but it adds up quickly, especially when you are putting water in with hardness and alkalinity. With the Minima I fill the service boiler with approx 1700ml distilled water. Over the course of 4-5 weeks steaming approx 1 big jug a day (40 seconds of steaming approx) the boiler will need to be drained because from that point you’ll start to see scale building up.
The point I was making about testing water from the steam boiler is alkalinity and hardness reduce as scale is formed until scale stops forming, so no matter what happens when you test the water you’ll conclude it won’t form scale. Of course, you’ll see it’s right on the edge/just a little over limit. In your case, you can track how close it is to forming scale as alkalinity and hardness both rise over time, but you can’t perform a random test and know when it started to scale if it gets beyond that point.
LMSC So, for scale to become an issue, we need to steam a few times a day, leave the water to sit in the boiler, not draw something out regularly and do not flush out the water and replace once in 5-6 weeks.
Even doing this scale probably won’t be an issue for quite some time. I used Volvic in the old Expobar for months without descaling and didn’t have any issues.