1.2. When a provision of this Regulation requires that water undergo a disinfection treatment, that treatment must be administered in a way that ensures at all times or, as the case may be, during the period prescribed by the provision, a constant presence of the disinfectant at the concentration, level or rate fixed by that provision, or, in the absence of such parameters, at a concentration, level or rate sufficient to ensure the elimination of pathogenic microorganisms with an effectiveness at least equal to the elimination percentage provided for in that provision.