Some cleaning machines are designed for cold water extraction so if your instructions do not say to use hot water don't. In addition, if your hot water is too hot, it can scald you when filling the tank, or if the machine breaks, hot water may leak out and burn you as well. Cold water also works better on protein stains like blood, milk and eggs, according to Ohio State University.
Using Hot Water
Hot water helps loosen dirt and works best for most stains and carpet types. Combine hot water with a carpet cleaning solution and you will clean your carpets without hiring a professional.
Unless you're cleaning a protein stain or have a cold water only extraction machine, use hot water to clean your carpets. According to the University of Missouri Extension, turn your hot water heater no hotter than 48.9 degrees Celsius to keep you and your family safe.