Valuation of the costs incurred by consumers due to a decrease in tap water quality would provide valuable insights to policy makers. In this paper, we present and implement a method to infer the value for consumers of the quality of supplied water. Our approach uses concepts developed in the literature of environmental good valuation and the literature of equivalent scale measurement. Our application to French data covering the eighties proves that we approach is tractable : it only uses usually available data and it gives rather intuitive results while relying on reasonable assumptions.