Originally Posted by pmsherman
Bernoulli's theorm most likely doesn't apply here because the fresh tank overflow is supposed to have a self closing fitting on the end of the tube. My overflow tube has a squashed rubber hose at the bottom end of it. When there's no water in the tube, the hose is flat and doesn't present an opening for air to flow over. Once water starts flowing out of the tube, the siphon effect keeps it going until the tank end of the overflow is above the water level.
Break the siphon and it'll never drain the tank. You will, however, still get some overflow caused by sloshing of the water in the tank.
Also, you'd need a real "nozzle" to get the air moving fast enough to provide enough suction. Normal air flow over the end of a tube won't suck water. (It might whistle, though!)
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