Especially since the recognition of the Right to Water (rtw) by the United Nations General Assembly in 2010, the rtw debate has largely been a discussion about implementation issues. Taking an institutional economics approach, the present study works on the basis that implementation deficits are not primarily due to reluctance on the part of actors in the field of water policy, but to the factual issues themselves. It focuses on two requirements: Firstly, it is also important to take seriously those sustainability objectives of water policy that may militate against strict implementation of rtw (efficiency, ecological sustainability, refinancing). Secondly, the medium under consideration, namely "water”, has to be regarded as a supply service with a package of properties including not only quality, but also availability in space and time.

Against this background it is evident that while there are hurdles to access for the individual user, these at the same time possess specific functions with regard to competing water policy objectives. To a certain extent, therefore, hurdles can be regarded as legitimate. From a normative point of view, the question arises as to what kind of hurdles can be regarded as legitimate, and how high these hurdles can be. We take the view that hurdles to access must satisfy the three test criteria: functionality, reasonableness of burden and non-discrimination. This leads to the new concept of "sustainable access".

In our opinion it is the task of future rtw research to explore on this foundation the limits of rights violations as closely as possible. This results in far-reaching opportunities, especially for practicable implementation of a rtw in practice. The extension of the access definition to take in the criterion of functionality, and the hurdle perspective presented here, lead to better assessment of the supply situation in practice, supply concrete approaches to improving it, include potential resistance right from the start, and thus honour the claim of the SDGs to take equal account of social and sustainability concerns.