Hot tap water, real harm?

OK so there has been many stories about how the hot water tank that goes to the hot tap is more soluble to lead and other metals. Also they say that there is a lot more bacteria in these hot water tanks. Now I understand that maybe you shouldn't always drink from the hot water tap, but what is the harm in having a gl of hot tap occasionally. Are you going to get lead poisoning from one gl of hot tap water??