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This article examines the causes and addresses the prevention of unintended interconnections, particularly cross-connections, in novel urban water systems using the example of Qingdao, where a Resource Recovery Centre for the reuse of greywater and blackwater has been established for 12,000 inhabitants. With respect to cross-connections, this work incorporated both social-scientific and technical error analyses. The social-scientific error analysis systematically focused on the planning, implementation, and operational phases of the project. Organisational shortcomings were identified in four areas: (A) Coordination and consensus between the commissioned design institutes, (B) information in tenders, expertise, and awareness, (C) ownership by investors, and (D) time management. Based on empirical evidence, this article derives and discusses (eight) recommendations for good management, integrating technical and organisational measures aimed at preventing cross-connections. The pursuit of such measures is appropriate in order to prevent most types of misconnections — not just for the case under discussion, but for other novel urban water systems as well.