Unable to answer "What diameter is specified on the sign for this fire hydrant?" for https://osm.org/node/9785901875 via StreetComplete 51.1:

Nie widzę tabliczki, ale są jakieś napisy.

Attached photo(s):
https://westnordost.de/p/136124.jpg
https://westnordost.de/p/136125.jpg
https://westnordost.de/p/136126.jpg