What about have some way to sense weight on the seat? Maybe have the tank fill only partially until there is a significant weight (say, over 25lbs or so) on the seat, at which point the tank continues to fill. It can be designed so the weight of the lid is not enough to activate it. (One drawback is that it might surprise someone who is not expecting it.)
Or what about a solenoid connected to the exhaust fan that activates the mechanism?
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Allie Moore and I have a combined carbon footprint much smaller than that of one average American...
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