The invention relates to a method for improving the transmission of ultraviolet rays emitted by a lamp inserted into a quartz tube used in a device for disinfecting water using UV light. The purpose of the method is to prevent the deterioration of ultraviolet rays as they pass through a gaseous médium, in particular air. This results in the improved efficieney of the disinfection device and reduced power consumption. The method is based primarily on removing the air from the space inside the quartz tube that surrounds the ultraviolet ray emitting lamp and subsequently introducing another gas therein.
