Do it yourself

While visiting relatives over the weekend, my roommate's father mentioned that he'd just drained the sediment out of his water heater, and therefore the hot water was really hot. Why should having sediment in the water heater cause the water to be less hot? Less of it, maybe, but to make it less hot? And in any case, how does one drain the sediment out of a water heater? He's offered to do it for us, but he's in his 80s, and we'd rather tackle the job ourselves (not to mention he probably won't be visiting until much later in the spring). Jeanne