This article is about a brief controversy that erupted in 2015 around the City of Montreal’s plan to divert 8 billion liters of raw sewage into the St. Lawrence River while it conducted critical maintenance on its sewer infrastructure. In the end, though, the Flush was non-eventful: It went ahead as planned and with no lasting effects or complaints. We suggest that the best way to understand how the City averted the crisis is through the concept of ‘affective maintenance’. If infrastructures are meant to be uneventful (i.e. narratively stable and generally lacking in surprise ruptures) then the maintenance of public affect is as important to their functioning as the physical work that keeps sewage flowing in the right direction.