This article extends ecological framings of resilience into socio-ecological and governance domains for urban infrastructure managers concerned with climate risk. Under moments of disruption, reliable and equitable access to adequate provision of public goods is anticipated to be increasingly challenging in cities across the world due to observed and anticipated disruptions of climate change and variability on city-wide infrastructures. Many cities facing such conditions are seeing rapid population and infrastructure growth enhancing exposure and vulnerability. One such example of disruptive climate risk is enhanced water scarcity. Private responses to the Cape Town drought adopted off-grid water technologies in order to secure their own supply while curtailing their dependence on the public water system. Unintended consequences of the nascent off-grid capacity created by private actors precipitated system transformations and accommodation challenges to disrupted public systems. The novel capacity generated through these responses to urban risk demonstrate what is identified here to be ‘partial functional redundancy’ – a key expression of resilience. Such response actions demonstrate partial and pragmatic expressions of redundancy through types of reserve capacity as a source of resilience in response to water insecurity.