I'm looking at a vent that will be used to prevent a tank from collapsing due to vacuum pressures in a pipe burst/free drain scenario. The situation would be a container is filled with water when an inlet or an outlet pipe bursts. The water flowing out would create some pressure in the tank that would need to be balanced by some vent(s) at the top of the tank. So here's an equation that I have on file: Av = Q/(4005*Ce*sqrt(pressure differential)) It's not a matter of if I can plug and chug my way through this - it's a matter of finding out WHERE this equation comes from. Nobody I've spoken to has any idea, nobody around my office seems to know, and really, it's not OK to use an equation without knowing it's validity nor it's origin. Does anyone have ANY clue if this equation will suffice or information regarding it's origin? I need some sort of legitimate reference, but I just can't find a darn thing. Much appreciation!