Abstract: The present valve, employable by persons affected by hydrocephalus, permits discharge into suitable offtake branches of the excess cephalorhachidian fluid existing in the ventricles of the brain. The valve basically consists of a hollow cylindrical body (1) having inside a seat (5) with an enlarging triangular shape designed to interact with an aptly-shaped capsule or small piston (6) and placed against an antagonist spring (7). This pattern permits to offset the varying amounts of ventricular fluid pressures, discharging outside any fluid, whether large or small, through suitable offtake branches and at the same time it accomplishes a self-cleaning function which ensures a constant flow efficiency.