I have an application that is drawing fluid from a reservoir via a standard dip tube. This application has a special requirement that once the fluid is depleted from the reservoir, the pump pulling liquid from the reservoir needs to shut off before drawing air into the system. 

The function of this type of valve would be more or less the opposite of a floating shutoff valve used in toilet tanks where the floating mechanism closes the valve once the tank is filled. My application would do the opposite, where the float closes a valve on the dip tube or shuts of the pump once the tank is empty (or close to it).

Does anyone know if this type of valve exists on the market, or is it something I need to design on my own? Thanks!