This exploratory article considers the accumulations of fat and other materials in London’s sewerage system – known as fatbergs in the UK – in terms of the processes of infrastructuring. In particular, drawing on a range of media, including a major museum exhibition, numerous newspaper and online articles, and a TV documentary, this article analyses how London’s fatbergs have been affectively enacted. The affects identified include: disgust in the composition of the fatberg, pride in the London-ness of the fatbergs, admiration at the ‘flushers’ courage, generic horror at the sewers, shame in the flushing of wet wipes, and anxiety about microbial threats. Such enactments simultaneously perform the fatbergs, the sewerage infrastructure, and the public audiences, through what we can call ‘affective infrastructuring’. This extends the analysis of infrastructuring to encompass the ways in which public audiences are affectively ‘made’. The article also suggests that the various affective enactments of the fatberg cumulatively perform London as spatially uniform and the sewerage system as temporally naturalized. A critical implication of this is an effacement of, on the one hand, class and cultural difference and, on the other, historical specificity.