End of life indicator for automatic toilet cleaning devices

摘要

An end of life indicator for use in a toilet cistern with an ambient solution containing an active disinfectant component. The end of life indicator comprises a core of water soluble dyestuff surrounded by a polymer resistant to bleaching by said disinfectant solution. Upon the depletion of the active disinfectant component surrounding the end of life indicator, the alkalinity of the solution increases to a predetermined level whereupon hydrolysis of the polymer coating continues until water penetrates or dissolves the coating sufficiently to come into contact with the water soluble dye.