A drinking water dispenser with built-in UV sterilization system comprising a housing and installed in the housing: a device for connecting to a water source; a tap for dispensing cooled water to consumers; a cold water tank equipped with a cooling device and having a lower part to be filled with water and an upper part where an air cavity is formed when the tank is filled with water, wherein the cold water tank has an inlet for water coming from the source connected to the device for connecting to the water source, at least one UV radiation source is installed inside the cold water tank, the cold water tank has a cooled water outlet connected to the tap for dispensing cooled water to consumers, wherein the dispenser additionally contains a flow sterilizer having an inlet and an outlet, the cold water tank is additionally equipped with an outlet for uncooled water and an sterilized water inlet, the inlet of the flow sterilizer is connected to the outlet for uncooled water, and the outlet of the flow sterilizer is connected to the sterilized water inlet, characterised in that a funnel having a wide upper part and a narrow lower part is installed inside the cold water tank, wherein the funnel is installed under the inlet for water coming from the source, so that an upper edge of the funnel is above the water level in the tank, to isolate water in the lower part of the tank from unsterilized water coming from the source, and the narrow lower part of the funnel is connected to the outlet for uncooled water. a device for connecting to a water source; a tap for dispensing cooled water to consumers; a cold water tank equipped with a cooling device and having a lower part to be filled with water and an upper part where an air cavity is formed when the tank is filled with water, wherein the cold water tank has an inlet for water coming from the source connected to the device for connecting to the water source, at least one UV radiation source is installed inside the cold water tank, the cold water tank has a cooled water outlet connected to the tap for dispensing cooled water to consumers, wherein the cold water tank has an inlet for water coming from the source connected to the device for connecting to the water source, at least one UV radiation source is installed inside the cold water tank, the cold water tank has a cooled water outlet connected to the tap for dispensing cooled water to consumers, wherein the dispenser additionally contains a flow sterilizer having an inlet and an outlet, the cold water tank is additionally equipped with an outlet for uncooled water and an sterilized water inlet, the inlet of the flow sterilizer is connected to the outlet for uncooled water, and the outlet of the flow sterilizer is connected to the sterilized water inlet, characterised in that a funnel having a wide upper part and a narrow lower part is installed inside the cold water tank, wherein the funnel is installed under the inlet for water coming from the source, so that an upper edge of the funnel is above the water level in the tank, to isolate water in the lower part of the tank from unsterilized water coming from the source, and the narrow lower part of the funnel is connected to the outlet for uncooled water.