The fourth Mishnah in Maseches Shabbos relates an incident involving the people of Teverya. The people of Teverya had access to the hot springs of Teverya - naturally hot water. Before Shabbos they brought a pipe of cold water and passed it through the hot water of the springs, so that on Shabbos they would be able to use the water that had been heated inside it.
The response of the Sages:
The Sages told them that this is not permitted. Even though the pipe was set in place before Shabbos, the cold water flows and is constantly renewed inside it, so that fresh cold water is being heated on Shabbos itself. Their status is therefore that of water heated on Shabbos.
Heated on Shabbos: Such water is completely forbidden for washing - even a single small limb and even with a small amount of it - and of course it is forbidden for drinking as well. This is unlike water heated before Shabbos, which may be used for washing one's face, hands and feet.
Heated on Yom Tov: Such water is forbidden only for washing the entire body, but one may wash his face, hands and feet with it, and it is permitted for drinking as well - since on Yom Tov it is permitted to heat water for drinking.
When the people of Teverya heard the words of the Sages, they broke the pipe, as the Gemara relates, and no longer made use of it.
The muliar and the antichi:
The continuation of the Mishnah deals with two vessels used for heating water, and the distinction between them lies in the structure of the vessel:
"Muliar" - a vessel best described as resembling a Russian samovar: the coals are placed in one compartment and the water in another. When it is swept out, meaning that the coals were removed from it before Shabbos, one may drink from it on Shabbos, even though the water was heated by the coals.
"Antichi" - a vessel similar to the muliar, except that the coal compartment is located beneath the water, at the bottom of the vessel and in its base. The body of the antichi is far hotter, and therefore even if it was swept out, "ein shosin heimenah" - one may not drink from it on Shabbos, because it continues to heat the water even after the coals have been removed.
It emerges that the reason for the distinction is one and the same: in a muliar that was swept out, the water was heated before Shabbos, whereas in an antichi the water continues to be heated on Shabbos itself, and for that reason it may not be used.
In summary: In this Mishnah we learned the law of the pipe that the people of Teverya brought into the channel of hot spring water - that its status is that of water heated on Shabbos, which is forbidden both for washing and for drinking, and like water heated on Yom Tov, which is forbidden for washing the entire body but permitted for drinking. We also learned the distinction between a muliar that was swept out, from which one may drink, and an antichi, from which one may not drink even when it was swept out, because the water continues to be heated on Shabbos itself.