Strongly dominated by natural science disciplines (as civil and hydraulic engineering, irrigation studies, hydrology, climatology, and soil sciences), conventional thought characterizes water control technology as morally and politically ‘impartial’ – a tool to be used, a means to a desired end. In this paper we challenge this view by showing how technological artefacts are scripted or coded by human agency, social norms on right and wrong, and power relationships, and how they, in turn, ‘structure’ or ‘mediate’ the moral actions and decisions of human beings. We discuss at length what technology is, how its designs are inherently social, and how the social coordination of labour as well as technology's replicability are central for it to emerge and exist. Through a case study about tank irrigation in India, we demonstrate how the moral agency of maintaining a certain social order in the tank-irrigated area was delegated to technological designs of sluices, waste weirs, and other discharge structures, but also to the layout of canals, and the landscape of the command area. Precisely this delegation of the reproduction of social order to material structures allowed the sustaining of differentiated power relations over a long period of time. In conclusion, we claim that our argument has much larger relevance for the politics of water control technology, even for mega-technology such as large dams. We claim that engineers and planners not only shape material designs of water control structures but that they implicitly ’materialize morality’. In that sense, re-organizing water rights and re-distributing water resources is not merely a matter of redressing institutional policy frameworks but equally involves re-moralizing and re-politicizing the very material technological artefacts.