The amount of water you’ll need will depend on what you’re cooking. For most purposes, one cup should be enough. However, if you’re making pasta or potatoes, you’ll need more. Knowing how to boil water in an Instant Pot is one thing. But you still need to know how much to boil! 1 cup of water for pasta. 2 cups of water for potatoes. 4 cups of water for eggs. 6 cups of water for chicken or fish.