International audienceIn the French water sector, some large cities have put an end to public service delegations entrusted to private operators and have chosen to return in public control, which may seem surprising in view of the new public management advocating the private sector model. In a water sector, a “natural monopoly” marked by strong moral hazard, information asymmetries and many uncertainties, public service delegations continue to raise serious governance issues both theoretically and empirically, despite more restrictive regulations. A three-year intervention-research in a new régie, public operator, contributed to the implementation of management tools. The multiple data collected (documents, interviews, participant observati...