If you're flushing a toilet in the US , you're probably accustomed to that characteristic whoosh as a jet of water fills the bowl and then siphons down the contents with a dramatic gulp. In Europe, on the other hand, the process looks much different. There's almost always an option for a lighter or stronger flush, depending on what you need. And the water doesn't suction, but instead simply shoves the waste down. For a true contrast, in Germany and the Netherlands , sometimes the waste lands on a ceramic shelf that sits directly above a pool of water. All this potty talk isn't just impolite dinner table conversation. How our toilets flush has significant ramifications for water supply. It's an increasingly urgent issue in the US as climate change worsens drought , and many communities confront water scarcity across the country, particularly in the western states. The nation's unique siphon design once required gallons of water with each flush to create the suction effect.…