Status post sternotomy, coronary artery bypass grafting x2, a pleural effusion was drained on the right chest and 2 24 fr mediastinal blakes were placed anterior and posterior.On arrival from or to icu, intesive care unit regsitered nurse (icu rn) noted the leak in one of the two drains, rn thought it was the bulb, replaced the bulb, leak continued surgeon aware and exchanged the channel tubing, small crack found in tubing.No harm to patient from this event.