The Yuzamashi or Water Cooler is a tea service accessory to adjust the water temperature.

When brewing Sencha, pour boiled water into the Yuzamashi, then pour the water into the Kyusu. By doing this, the water will become the ideal temperature for brewing Sencha or Genmaicha, 176F (80C).

When brewing Shincha, pour boiled water into the teacup once, then pour the water into the Yuzamashi. Finally, pour the water into the Kyusu. The water will become the ideal temperature for brewing Gyokuro, 158F (70C).