Abstract: An improved dosing valve for use in beverage dispensers, toilet tank additive dispensers, and the like which dispensers comprise substantially rigid reservoirs. The improved valve comprises an air-lock seal and another seal which may also be an air-lock seal. Dosing valves comprising such air-lock seals are particularly effective for obviating leakage of low viscosity, low surface tension, wetting type products such as toilet tank disinfectants comprising surfactant material. The seals are so disposed that the valve will dispense a metered dose of a liquid product from its associated reservoir each time a moveable component moves from an UP position to a DOWN position, and a dose-volume of air will be vented into the dispenser reservoir each time the moveable component is moved from its DOWN position to its UP position. The moveable member can be moved upwardly either mechanically, or by virtue of being buoyant, and it can be moved downwardly by gravity alone or by gravity supplemented by biasing means.