A:Answer Hi Terrifrmtx - Thanks for considering GE Model GDF630PSMSS! This model has Automatic HotStart and will preheat the water. Water coming into the dishwasher may be as low as 95 degrees F and this feature will help raise the temperature to the required 120 degrees F. It actually heats the tub, spray arms, dishes, (prior to the main wash cycle) allowing proper cleaning. Once selected, approximately 1-1/2 gallons of water enters the tub, circulates in the tub for 5 minutes and then drains. This helps to purge cold water that may be in the line. Then another 1-1/2 gallons of water enters the tub and circulates for approximately 15 minutes and then drains. The heating element is on during this period, heating up the water and the tub. After this option is run, the dishwasher will automatically go into the cycle that has been selected. Keep in touch at GEAppliances.com. Sue