In this article I explore the political and technical controversies of measuring water leakages in Mumbai to demonstrate how the dense historical accretions of technology, material, and social life that form hydraulic infrastructures in Mumbai trouble the audit cultures of neoliberal government. While scholars have recently drawn attention to the generativity of ignorance in the making of the state, in this article I argue that ignorance is not only a technology of politics, produced and managed by municipal water engineers and their subjects. Leakages, and the ignorances of leakages, are also enabled by the vital materiality of the city’s infrastructure. As engineers work hard to improvise resolutions to the leakages they can fix, and ignore the thousands of others they cannot, the processes of leakage always exceed the control of the city’s government. As such, the uncertain appearances of leakage in Mumbai not only provide the grounds for the work of the state. Leakages also constantly disrupt governmental projects in ways that make the water department vulnerable both to the claims of marginalized subjects and to new reform projects in the city.