Sure, if you reduce the pressure enough, water will boil at room temperature. But if you are talking about cooking or purifying water, it won't help. It is the temperature that matters for cooking or purifying (killing bacteria). The actual boiling or vaporization point of water has nothing to do with it. On the opposite end of the scale, raising pressure raises the temperature at which water boils, which is what a pressure cooker does. At sea level pressure, you can't get water hotter than 212 degrees farenheit, but by increasing the pressure, you can get water much hotter which is why a pressure cooker can cook foods faster, or break down foods that need a higher temperature than the normal boiling point of water.