Aeration Valve

thingiverse

Aeration Valve which can be inserted into sewage drains to prevent siphoning. This is especially relevant on boats where siphoning can flush outside water back into the ship and can lead to sinking. When water comes in from the bottom side of the valve, the ball, which floats, will block the exit at the top and the water cannot flow through the valve. When the water pressure dropt the ball falls down in the seat and the valve allows air to flow from the top of the valve to the bottom. This prevents siphoning.