Electric water boiler

An electric water boiler, also called a thermo pot, is a consumer electronics small appliance used for boiling water and maintaining it at a constant temperature. It is typically used to provide an immediate source of hot water for making tea, hot chocolate, coffee, instant noodles, or baby formula, or for any other household use where clean hot water is required. They are a common component of Japanese kitchens and the kitchens of many East Asian countries but are found in varying use globally. Some thermo pots are designed with a feature that can purify water.
Black tea is typically steeped at 
while green tea is steeped at under . A number of thermo pot models offer an adjustable target temperature.
Components.
An electric water boiler consists of a water reservoir with a heating element at the bottom. Some models offer multiple temperature settings. Other models are part of larger water systems that boil water and provide hot, cold, and lukewarm water. Water may be dispensed in various ways, e.g. by pouring, an electric pump or by pressing a large button that functions as a diaphragm pump. Electric water boilers have a built in thermostat that detects when water has reached its boiling point of to automatically shut off.
Sedimentation.
Sedimentation is the accumulation within the water reservoir of natural minerals that exist in trace amounts in municipal water mains, mainly calcium carbonate. Heating the water causes the minerals to separate and fall to the bottom of the reservoir. This buildup can eventually create a variety of noises in gas boilers, reduce the efficiency of the unit and give rise to a sulfur (or rotten-egg) smell. Vinegar can be used to descale electric kettles.