All these years I have been cooking with cold water because I was under the impression (damn you, 5th grade science teacher) that cold water boiled faster than hot water. I have no idea why I was told that, or why I believed it for that matter but I did. The truth is, cold water does not boil faster than warm water, but that is beside the point.
So should we all be cooking with warm water to speed up the process? Think again. Never cook with or consume water from the hot-water tap. This is because hot water dissolves more lead more quickly than cold water, which means you may be consuming more lead than you should be. Houses built before 1986 are the most likely to have lead parts, however even plumbing legally considered lead-free today may contain up to 8 percent lead. While copper pipes replaced lead ones decades ago, fusing pipes with lead was legal until 1991.
Why does it matter? Well, too much lead in the body can cause serious damage to the brain, kidneys, nervous system and red blood cells (it's especially bad for pregnant women and children). So the EPA recommends that you do not use water taken from the hot tap for cooking or drinking, and especially not for making baby formula. If you need hot water, draw water from the cold tap and heat it on the stove. Anytime a faucet hasn't been used for at least six hours, "flush" all the water that has been sitting in the pipes. This could take anywhere from 5 seconds to 2 minutes. When the water stops getting colder, it is "flushed."