Abstract

A passive dosing dispenser for issuing, for example, a volume of a toilet tank additive solution into a toilet tank as the water is draining therefrom while the toilet is flushing. A preferred dispenser comprises a product chamber for containing a quantity of a solid type product which can be dissolved in water to form a toilet tank additive product solution, a solution reservoir for containing a quantity of said solution in fluid communication with said product chamber, an inlet/discharge conduit having its lowermost end in fluid communication with said solution reservoir and its uppermost end in fluid communication with a syphon tube, a first air trap disposed adjacent said inlet/discharge conduit for trapping an air bubble that is used for isolating said product solution from the toilet tank water in the syphon tube during quiescent periods, a second air trap disposed adjacent the syphon tube for retaining the air bubble while the water is draining from the toilet tank during flushing, a discharge reservoir disposed at the outlet end of the syphon tube to retard the discharge of the toilet tank additive product solution so that the discharge requires a predetermined period of time, and an air vent in fluid communication with the solution reservoir and the product chamber.