feed-tank

from The Century Dictionary.

• noun A reservoir or vessel in which the water to be supplied or fed to a steam-boiler is contained. The water may be hot or cold: when hot the tank is usually closed to prevent loss by evaporation.
• noun A reservoir or vessel designed to hold liquid fuel, such as kerosene or gasolene, which is to be fed to a burner.
• noun A reservoir or tank containing reagents, or raw materials, which are to be fed to a vessel in which some chemical or manufacturing process is conducted.