Abstract: An open hot-water heater includes a water tank; a hot-water overflow extending from the water tank; a faucet connected to the hot-water overflow; and a cold-water supply arrangement for introducing cold water into the water tank to refill the water tank and to drive hot water therefrom through the hot-water overflow. The cold-water supply arrangement includes a cold-water inlet coupled to the water tank and a cold-water discharge pipe connected to the cold-water inlet and having an outlet opening situated in the tank for introducing cold water into the tank. There is further provided a tank volume varying device and a valve assembly exposed to cold-water pressure prevailing in the cold-water inlet.

Abstract: A hot water heater includes a water tank defining a tank space for accommodating water; a cold water inlet and a hot water outlet connected to the tank; a hot water tap in the hot water outlet for controlling flow of hot water from the water tank; a cold water valve in the cold water inlet for controlling flow of cold water into the water tank; and a volume altering device for changing the tank space.