@futagoza: Thanks. I thought that is watertight (without holes). My bad. It wasn`t. Watertight term is from polygon modeling - especially for 3d printing (stl). It means that surfaces have no holes. This is mainly for closed shapes but I used it to surfaces. Maybe I used it wrong to open mesh but I thought about surfaces.

@Finema: Thanks a lot. How have you found that points (some command to find broken edges or not connected points)?