That will solely depend on the instructions for your particular product. That is why you should always read the guidelines before brewing your first pot. It is most likely that the instructions will recommend using cold water with your moka pot. The unit will use the heat to get the water to the right temperature, which means that it is not something you should worry about. You may want to use filtered water with your moka pot. It will deliver the best coffee taste, but it will also minimize buildups in the filter and other unit components. That way, you can extend the longevity of the pot, and time between deep cleanings.