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  • I recently took an airplane trip and, as occasionaly happens, had to use the tiny little
    facilities while in the air. The instructions on how to flush reminded me of being on a submarine.

    In the navy they call it “the head” for some obscure reason. Actually the reasons not so obscure; the term comes from the days of sailing ships when the place for the crew to relieve themselves was all the way forward on either side of the bowsprit, the integral part of the hull to which the figurehead was fastened. On a submarine all the human waste from the head drops into a sanitary tank. It is done in a clever way by opening a water valve to flush while simultaneously pulling a huge handle attached to the bottom of the bowl. This opens a ball valve allowing the waste to flow into the before mentioned tank. You then close the ball valve with the huge handle and turn off the water supply leaving a nice watertight seal in the bowl. Easy, right? It doesn’t take long to get the hang of this procedure, but at 2 in the morning one can forget to open the water valve and a terrible odor wafts up.

    Now to the fun part. Every so often the sanitary tank gets near its capacity and must be flushed out. Usually this is done on the mid watch (12 to 4am) to limit the inconvenience to the crew. Flushing the tank requires that you know the depth the submarine is operating. For every 100 ft of depth the outside water pressure is 44 lbs per square inch. This means you have to pressurize the tank more than the outside pressure before opening the outer valve. Normally you keep the pressure a good deal higher the entire flush cycle. This only takes about a half an hour and then you can close the outer valve again. The extra air pressure left in the tank must be ventilated through some charcoal filters before anyone can use “the head” again. Another half an hour for that. So the entire operation takes about an hour. Meanwhile the “blowing sanitary” signs are hung on each head so no one can make a mistake.

    Wrong! At least once a patrol some poor half asleep sailor makes the mistake of trying to relieve himself with his eyes shut. He has to have his eyes shut to miss the signs and not notice the bubbles leaking through the watertight seal in the bowl. The minute he pulls the large handle toward him, it is too late to correct it. Whatever is left in the sanitary tank flies in his face at about 60 psi no matter how fast he is with the handle.

    Submariners are a proud lot and we even give an award for “Venting Sanitary tanks inboard”.

    I’ve been close, but never was awarded that one.
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