Once you drain or flush your hot water tank, it needs to be refilled before you can turn the power and gas back on to the unit. Electric hot water tanks must have a full tank of water before powering the heating elements. This prevents the elements from overheating and burning out. Refilling a hot water tank also requires removing the air from inside the empty tank. Before refilling the tank, ensure that the power is off to the unit.
Remove the draining hose from the drain valve. Turn the drain valve clockwise to close the valve. If you opened the temperature relief valve to help drain the water, flip the valve handle down close the valve.
Turn on the cold water supply to the hot water tank. The supply valve is either a rotary knob that you turn counterclockwise or a lever handle that you turn in the same direction as the water pipe.
Go to the nearest tap and turn on the hot water. As the tank fills, water and air will come out of the tap spout. This is how you expel air from the tank as it is filling.
Check around the bottom of the hot water tank for leaks. Tighten the drain valve knob if necessary.
Turn off the hot water handle on the tap once water is flowing through without any spurts of air. Turn on the electrical circuit breaker to the hot water heater inside your fusebox. If you have a gas hot water heater, light the pilot according to the manufacturer's instructions.