This invention refers to an Automatic/Manual Device for Controlling Outflow of Water or any Fluid with Functioning and Easy Installation. It has a threadable intake nozzle for the inflow of water or any other fluid. The nozzle can be turned to direct the device as needed. Also, in the interior of the device there are two magnets with inverse polarity a spring, two rubber membranes with orifices, a rubber membrane without an orifice, two supports for said membranes, an air chamber, a manually-activated metal ring, a functioning mechanism with the following positions: ON-OFF a double copper tube with the air chamber, and an activating mechanism with "manual" and "automatic" positions for operating the device. The functioning of this invention is provided for, with the objective being to shut off the flow of water or any other fluid once the container, tank, trough, barrel, tub, bathtub, toilet, pool or other reservoir has been filled, by way of hydrostatic pressure exerted by the water container itself through the double copper tube connected to the air chamber by way of the rubber hose, with the necessary pressure being exerted to separate the magnets and this close the fluid flow orifice.