We've never been big on pre-washing, but we also didn’t have a dishwasher for a couple of decades when we lived in Mexico. When we came to the United States and could use a dishwasher, we always let the dishwasher do the work and wash the dirty dishes. However, Whiskey (Marianna's dog) thinks pre-rinsing is a very good idea and is happy to pull his weight in that department!
Your dishwashing detergent actually likes food
As it turns out it really is best to not pre-rinse your dishes and let the dishwasher do its job. Remember, your dishwasher is a dishwasher and not a disposal, so you do need to scrape the plates and get any large chunks of food off, but other than that just pop the dishes in the dishwasher and you are finished with that chore.
Environmentally friendly dishwashing detergents use enzymes to break down fats, oils, and proteins on your dishes and remove all the food stains. Yes, this sounds a bit like a biology class because these enzymes are essentially digesting the food just like your stomach does! (We love science!) Enzymes in dishwashing detergents need food debris on the plates to attach to in order to work properly. Without any food on the dishes, enzymes just wash away and don’t have a chance to really clean your dishes.
The new dishwashers even have sensors in them that detect food particles, and they'll adjust the washing time and clean accordingly. There is no need to pre-rinse. Save your time and water and just scrape your dishes and then put them in the dishwasher.
Water use for hand-washing vs dishwasher
Today’s new, efficient dishwashers use only 4 to 6 gallons of water per load. You would have to hand wash your dishes really fast to beat that amount of water. A good rule of thumb is if you can hand wash your dishes in two minutes or less, you'll use less water than your dishwasher. If it's going to take you more than two minutes, then the dishwasher is the way to go. And of course, this goes without saying: try not to wash half dishwasher loads. Keep piling the dishes in there until it's full so you get the most efficient wash!