High capacity check valve bubbler keeps oil and air from being drawn into a system when negative pressure is developed. It is most often used when evacuating and purging apparatus with an inert gas.

The bubbler is filled with oil (mineral or silicone) to a level slightly above the top socket joint. Under negative pressure, the float is drawn up to seal the outlet and prevent back flow. When exposed to positive pressure, the float is pushed down opening the seal between the spherical ball float and socket joint providing for a high capacity outlet.