Hi. I need to know if it is possible for me to turn off the hot water supply by turning off the water supply to my hot water heater? I need to replace a hot water supply valve under a sink. I take it after I turn off the water supply to the water heater, I would have to drain the tank. My concern is, if I turn off the water to the heater, would the hot water heater burn up??? Can the hot water supply be shut off using this method? Any replys would be appreciated. Thanks in advance.