What is a one-sentence summary of the following article?
Near the drain valve where the hose is connected is a knob or lever that opens and closes the valve. Turn the knob or lever to open up the valve. Make sure it's opened all of the way to allow for proper drainage. If the valve is difficult to open, use a wrench to help turn it. At the top of the water heater is a valve that allows air to flow into the unit in order to relieve pressure that can build up inside of it. Open the pressure relief valve to allow air to run through the valve and drain the water. If water doesn't start to flow immediately, loosen the nut on the top of the water heater that connects the drain valve to allow more air to pass through. Do not remove or entirely separate the nut at the top of the water heater. Just loosen it to allow air to pass through. Be careful not to snap or jerk the valves so you don't risk damaging them. It can take up to 30 minutes for your water heater to completely drain. When the water stops flowing from the garden hose, then the water heater has finished draining. Keep an eye on the garden hose to make sure it's draining properly. Sediment can collect at the bottom of your water heater so it's important that you run fresh water through it to flush it all out. Turn the water valve to start the flow of water through the heater so it drains through the drain valve. Allow the fresh water to flow for at least 5 minutes and then turn it off again.

Summary:
Turn the knob on the drain valve to open it. Pull up on the pressure relief valve at the top of the tank to open it. Allow the water to drain completely. Open the water valve for 5 minutes to flush out the water heater.