The first water from the tap is stagnant and contains lime scale

Circulation for cold water? Luxury, luxury.

Read the text again and then you will know that you wrote nonsense, it is about hot water.

Read the text again then you will know that you wrote nonsense, it is about the hot water

that the first cold water in the morning from the tap

Regarding the question: I have been doing this as always and I never liked the first water from the tap, neither with nor without descaling in the single-family house, multi-family house, holiday apartment, whatever. If it really is about 400ML, I also don't understand all the fuss here. Sorry, normally I am nicer, but this really sounds like a first world problem. Give it a try: Take a glass of delicious water (i.e. after it has run) and let it stand overnight. Does it taste as good to you the next morning as the day before?

Read the text again then you will know that you wrote nonsense, it is about hot water

May I return your compliment. I hardly believe that the person seeking advice draws a nice 55° water in the morning.

Regarding the question:
I've been doing it this way forever and I've never liked the first water from the tap, neither with nor without descaling in single-family houses, multi-family houses, holiday apartments, whatever.
If it's really about 400ML, I don't understand all the fuss here. Sorry, normally I'm nicer, but this already sounds like a First World Problem.

Try this: Take a glass of tasty water (after letting it run) and leave it standing overnight. Does it taste just as good the next morning as the day before?

Maybe I expressed myself wrong. It's not primarily about the amount of water for me, but whether this is "normal" or not. I never noticed this in previous apartments in this way and so I wonder why it's so different now. And why the water hardness is increasing again. The first thought I had was that something might be wrong with the plumbing installation and that's why I wanted to hear opinions about it.

By the way, regarding your test: I actually do that every day because I always put a glass of water by my bed at night. And if I take a sip of it in the morning, it doesn't taste as stale as the first water from the tap.

I can imagine that some limescale might still build up in the pipe or faucet even with softened water. If extremely low-lime water then sits in the pipe, it might dissolve limescale from the deposits again. As a non-chemist, I can't say whether this has anything to do with the high sodium content.

Our Berlin "concrete water" tastes quite good, even though it grits between the teeth. But I always let some water run because I like it cold.

, maybe I should still consider a circulation line for cold water ;-)

So I think it is normal to let water run before drinking it. I always like the taste of tap water better when it has run for 10-20 seconds beforehand. I actually overlooked that you also did a hardness test, which then turned out higher. I cannot explain this effect. I also cannot explain any "error" in the installation that would cause such a thing. Is the value then as high as the completely untreated water before the softening system? Or is the value somewhere in between?