PiergC

Hi All, I want to model a manholes in order to have only negative flow through it. I know it is possible to set the unidirectional flow using the "U" in the Type attribute of the 1d network; but it allow only positive flow (From upstream to downstream). I want to represent a manhole that only allow flow from the culvert to the 2d domain and not the opposite. Is there a way to represent it? Please let me know if my question is not clear. Many thanks, Piergiorgio