After installation, I realized that both spherical outlet valves are leaking. One dripped light and the second dripping every second.
I have the taps well flushed but it brought no change.
Can also be that I unfortunately caught a bad series.
Now I have mounted two of these: "Xclou 369,706 ball drain cock 3/4"
They are perfect and were even cheaper.
Therefore, I advise the purchase of from "Sirocco 05622462 ball drain valve 3/4 inch with grommet (difficult)".