How far is your water heater from your dishwasher. I knew someone who had to get a circulating pump. His dishwasher was so far form the water heater so when the dishwasher would fill, it used the cold water that is sitting in the pipes and by the time the hot water got there, the dishwasher didn't need any more water. the pump will keep the water circulating back and forth to and from the hto water heater. Or you an get one of those electric small heaters that heat on the spot as well.