The aim of the paper was an analysis of the structure of tap water consumption by rural households considering the use of its results for designing the elements of water supply and sewer systems. The analysis of this structure was based on direct measurements of water consumption conducted in 2011-2014 in 30 households located in Przeginia Duchowna village (Czernichów commune, Malopolskie province). Double measurement of water consumption (water supply connection or water draw off point outside a residential building) enabled the separation water consumption for household and additional purposes from the total water consumption per household. Analysis of the collected data revealed considerable disproportions between the real water consumption and stated in the design guidelines. Calculated on the basis of the study, averaging 85.6 dm3·I-1·d-1, accounted for only 57% of the value of 150 dm3·I-1·d-1 most commonly used in design. Because of the possible determining the water consumption structure it was demonstrated, that the divergences concerned also the volume of domestic sewage discharged from rural households. Obtained results revealed also that application of the principle, where the volume of sewage equals the volume of water consumption by rural households, for designing sewer systems is usually incorrect. In the analyzed household in fact, only 83.1% of the volume of waste water was discharged in the form of waste water to the sewage system. The remainder was called. non-returnable water consumption for additional purposes.