If you're one of those people who pre-rinses their dishes before putting them in the dishwasher, you're wasting water. The most efficient dishwashers now use close to 2 gallons to clean a load of unrinsed plates and are designed to remove dried food on plates, allowing you to wait until the machine is full to run it. And if you only have a few dishes to wash? The dishwasher is still the best bet. A new study found that running the tap to wash a single place setting (a plate, cup, bowl, utensils, and some serving dishes) consumes about 3 gallons, so running a dishwasher for just two place settings still saves water compared to washing dishes in the sink.