On the reading of the curve, it appears that waters, from the sand filter, are characterized by high conductivity, which exceeds 500 mS/cm for the first outgoing fractions compared with the glass filter. The values of electrical conductivity of wastewater are always lower than those of the filtered water; they are included between 0.685 and 0.979 mS/cm and they are generally stable in the period from 7to 70 days. Conductivity curve is divided into three intervals, the first [1-5 days] it is a phase which is characterized by a remarkable drop in values of electrical conductivity for the pilot of sand compared to the glass filter; This is the phase of leaching of filters. In this phase we notice that the first series of measures are characterized by high electrical conductivity, including the first drops retrieved in parallel with the response time of the filters; These values are large at the beginning of the functioning of the filters because of the very high concentration of soluble salts. For the second interval of [4-13 days], we see a small increase in the values of conductivity with a slight change for the two filters. In the third interval [35-70 days], a decrease was noted for values around of the value of 1.7 mS/cm for the pilot of sand and 1.48 mS/cm for glass.