A newborn infant who could not be weaned from bypass after undergoing corrective surgery for atrioventricular septal defect was placed on arteriovenous extracorporeal membrane oxygenation (ECMO). Thirty-six hours later, a sudden violent gush of water was observed from the heater cooler system at the point where the outlet tubing had become detached from the machine. It was quickly established that this event had been caused by a massive pressure buildup at the integrated ECMO heat exchanger. A series of attempts were made to identify the cause of the problem and so rectify the situation: changing the heater cooler system, reversal of water flow through the heat exchanger, and, finally, insertion of a bridge between the outlet and inlet water tubing to moderate flow through the device. A complete circuit change-out and the associated risks were thus avoided, and the patient was successfully weaned from ECMO after 83 hours. Subsequent analysis of this incident identified three key elements as factors in this systems failure: heater cooler system cleaning protocol, heat exchange device construction, and incongruous heater cooler system application, which, together under these exact conditions, contributed to creating a situation with the realistic potential for a negative outcome.