Instant hot-water dispensers are simply miniature electric water heaters that serve only one faucet. Unlike a conventional water heater, however, the tank never becomes pressurized. The heated water expands, filling an expansion chamber in the upper part of the tank. When you turn on the faucet, more cold water is released into the bottom of the storage tank, displacing hot water in the tank and expansion chamber and forcing the heated water up through the faucet. Adjustment is needed only if the water is too cool or if it's so hot that it boils away, causing the tank to overheat.
Tanks vary in size and by the heating elements' wattage.
As will any water heater, hot-water dispensers may accumulate scale in hard water areas. Some units have drain plugs at the bottom to allow you to drain the tank once or twice a year. All rights reserved.