This paper addresses minimum utility cost mass-exchange network design by considering the special case of water minimisation. Two different situations are considered, re-use and regeneration re-use for single contaminants. For re-use, three different methods of targeting are presented, one of them being simultaneously a design method. This novel design method has the advantage of considering flowrate constraints only in the final stage of design. The concept of multiple pinches is introduced to prevent designing networks that do not lead to minimum cost distributed effluent treatment systems. For regeneration re-use, this paper presents the first known algorithm for targeting minimum water consumption in all possible situations. The targeted flowrate is then used to design the mass-exchange network, that almost always features splitting of operations.