Thanks to jomjol and his great work.
I printed this: https://www.thingiverse.com/thing:4573481 and realized, that this is not fitting my watermeter. Its a Sensus620- Wasserwerke Hamburg.

So this adapter now is completly fitting the watermeter without any tape or something like this.

Aditionally i created a "diffusor" for the bright white LED. It helps a bit.

Creality

Ender 3

No

No

0.2

15