When regeneration recycling is introduced in a water using network, both freshwater consumption and wastewater discharge can be reduced significantly. However, design and targeting of the water using networks involving regeneration recycling is more difficult than that of the ones involving reuse only. In this paper, a few relationships are developed between the regenerated concentration and the regeneration pinch, based on the mass and flow rate balances below the regeneration pinch. By citing the relationships developed, the regeneration stream targets for the water using networks with single contaminant involving regeneration recycling can be predicted when the regeneration pinch does riot change. A few relationships are obtained to predict the critical regenerated concentration, at which the regeneration pinch changes, for both normal and abnormal networks. The normal networks are those have no pseudo pinch points. The abnormal networks, which have a pseudo pinch point, feature that a slight variation of the regenerated concentration will cause change of the regeneration pinch point. The relationships developed in this paper can simplify the calculation of regeneration targets significantly. The relationships obtained also provide clear insights into the water-using networks involving regeneration recycling. (C) 2013 Elsevier Ltd. All tights reserved.