In that Bucharest hotel I've seen Sloan valve. Now I found it's name. It's also called a flushometer. In an around 1930 I found a thing like this called a sitometer - made in Germany. Quite complicated - it had oil into it! In a 1959 Romanian book I don't know if they give this model, but they say that systems do requires a lot of water.
But a flushometer, how the vacum is produced? It haves also an valve into the wall?
Don't tell me about sensor and taps. Washing your hands sensor taps can be really annyoing.
