If you're like me, you don't really think about how much water you use when you boil pasta. I just fill up a giant pot to make sure everything is covered. This might be overkill, though. According to Epicurious, you can probably stand to use a lot less water when you boil pasta. Photo by Naotake Murayama.
Based on a New York Times article from food author Harold McGee, Epicurious ran a series of boiling experiments in their Test Kitchen to see how well pasta cooks with less water. They wrote:
In a series of tests, they found that a pound [450g] of pasta, which is typically cooked in roughly five quarts [4.7L] of water, cooked just as well in half that amount. Then they reduced the water to a third of those five quarts [1.5L] — again, the pasta was fine.
They also tried a method that involved skipping the water altogether and cooking the pasta directly in the sauce:
This method, which is best for short pastas such as penne, requires adding enough water to the sauce to cover the noodles (the added water cooks out of the sauce as it boils).
This helps conserve a little water, sure, but it's also just useful knowledge to have on hand. Chances are, you don't need to fill up that pot quite as high. For more detail, head to their full post at the link below.
How Cooking Pasta in Less Water Will Save the Planet [Epicurious]