content: If properly implemented, this could act as a momentary "shut off", but not a permanent one. The hissing you heard when the guy was blowing through the impeding direction was most likely air leaks from the crappy 3D printed cover that just snaps on. A properly sealed one would have a higher through-put end to end, but would still be highly impeded. This "valve" wouldn't actually stop any fluid, but would greatly slow it down. Attached to the end of a garden hose for instance, it would reduce the flow to something you could likely drink from while aimed directly at your face - maybe like a water fountain.