פירוש על עבודה זרה 148:8

Rava says that a tank, which probably is another word for the vat into which the wine flows, must be scalded with hot water to kasher it.

Rava was sending empty jars from his place to other Jews in Harpania. He sealed these jars up well (some sort of double-seal) for he feared that the non-Jews with whom he was sending them would use them. Rava was of the opinion that just as the rabbis decreed against wine belonging to non-Jews, so too they decreed against storage vessels used by non-Jews, even for a short period.