The present invention relates to novel remotely dismountable valves comprising a valve body welded to the pipes and having a truncated seat, an outwardly truncated member fitting on said seat, an obturator whose movements may be remotely controlled due to an extension element and a heavy element made fast with the member via a cross-piece presenting an upper surface in the form of a segment of a sphere on which surface the likewise spherical surface of the lower face of said heavy element abuts.