Methods and apparatus for the slow, generally uniform addition of a disinfectant solution comprising an active ingredient, such as chlorine, to achieve a substantially constant level of active ingredient in the liquid of a grey water reservoir of a residential septic tank system prior to dispersal. A container configured to reside in a standard chlorine tablet dispenser is filled with a disinfectant solution, which contains a disinfecting substance as an active ingredient. A drip-valve is used to regulate the drip flow of the disinfecting solution out of the container and into the grey water reservoir.