Only a few seconds, although it depends on the quantity and type of waste. The sound of the disposer will change, when there is no longer any food waste in the grind chamber and the impellers spin freely. After all food waste is ground, turn off the disposer and let the water run for about 15 seconds to flush the waste out of the grind chamber and out to the water drainage/sewer pipes. Only a small amount of water, time and effort is required.