This paper studies the behaviour of the Tunisian consumer face their consumption of drinking water. The application of the contingent valuation method (CVM) from a statistical survey allows us not only to analyse the function of the demand for the drinkable water but also to determine the willingness to pay (WTP) of households. The creation of a hypothetical market enables us to carry out a program of improvement in the quality of the potable water and to ensure the follow-up of a sustainable management of the resource. The variation in the WTP is mainly due to the introduction of the variables that are related to the characteristics of the property and the socio-economic characteristics of the households. The results show that the household's WTP varies according to the nature of the physical quality of water and also to other variables such as income, housing occupancy, and the educational level of the respondents.