Water suppliers adopt a variety of strategies to gain access to and control of water resources. In contrast to theoretical approaches which assert that the status of ownership determines water supplier strategies, we argue that supplier strategies depend on the activation of property rights and the specific public policies applied to the resource. These two components of the institutional water regime are thus factors that are more important in explaining the suppliers' strategies than the intrinsic characteristics of the water operator. We thus present two case histories of aquifer exploitation for drinking and mineral water production; we compare two companies in Belgium, one publicly and one privately owned. This comparison shows that the operator strategy is identical in both cases, regardless of whether the ownership status of the water supplier was public or private. Both companies attempted to appropriate the resource privately in order to maximize its security over the resource and its supply. In each case, the winning strategy consisted in gradually excluding all direct or indirect users of the resource such as competitors, farmers and residents. The aquifer was then effectively protected in quantity and quality over time; however this state of affairs does not necessarily entail sustainability of the resource in a broader sense, as social and economic aspects were not directly considered.