A system for controlling the duration and volume of a flow of water in a flush of a Toilet, which includes a buoyant flush valve which is non-automated in user actuation thereof to a raised open position. The system includes a converting element, for converting the buoyant flush valve to a non-buoyant flush valve which is non-automated in user actuation thereof to a raised open position. A programming element enables programming of a controlling time, for controlling the duration and volume of flow of water in a flush of a toilet. A controlling element is connected to the programming element and the non-buoyant flush valve, for retaining the non-buoyant flush valve in a raised open position upon non-automated user actuation thereof to the raised open position, and for releasing the non-buoyant flush valve from the raised open position for closing the non-buoyant flush valve, within the controlling time.