After the hot water is used up, when the cold water starts coming, the water is rusty/urine color. Crown customer service says that may be there is sediment -- so I should flush out.
I need some instructions as to what precautions I should take, and how to flush out the sediment so hopefully this problem would be solved.

For long life and fewer troubles you should keep your heater clear of mineral build-up by FLUSHING NOT DRAINING on a regular schedule. Attach a hose to the boiler drain at the bottom of the tank. With the pressure on, open the boiler drain and let it run until the water runs clear. You will see a spurt of red,(rust) followed by white or yellow grains,(lime or calcium carbonate). This shouldn't take more then a few minutes.. Don't forget to flulsh every month. Your heater will thank you for it. Hope this helps and thank you for rating my answer, Tom

Thanks a million, Speedball1!