Embodiments of an apparatus for draining liquid generally include a liquid inlet, a p-trap, an additive reservoir, a fluid outlet, a float switch, a valve, and a fitting, wherein the liquid inlet allows for introduction of liquid, the p-trap allows for maintenance of a liquid level whereby contact is provided between the liquid and an additive contained in the additive reservoir, the fluid outlet is configured to maintain the liquid level above an additive reservoir bottom interior surface, the float switch provides indication of high liquid level, the valve allows for blockage of fluid flow between the p-trap and the liquid inlet, and the fitting allows for introduction of high-pressure fluid into the apparatus. Embodiments of a method for clearing a liquid draining apparatus generally include ceasing flow of liquid there into, operating a valve to substantially prevent reverse flow of liquid therefrom, and providing high-pressure fluid into the apparatus.