The application of magnetic treatment (MT) to raw water in water purification, mainly for the processes of coagulation, flocculation and sedimentation, is a new technology due to its economic and technical effectiveness. In this work, the effect of the effect of the magnetic field (MF) on the coagulation—flocculation processes, the influence on the formation of floccules at different doses of aluminum sulphate, and sedimentation using the Jar Test, for raw water prior to its potabilization treatment. It is concluded that there is a direct influence of the MF on each of the properties studied before and after the Jar Test (increase in pH when applying MF, decrease in conductivity, pH and turbidity after the Jar Test), under the established conditions of MF induction levels applied. MF induction levels applied (330, 276 and 240 mT). It is shown that MT has an impact on the coagulation-flocculation processes for the potabilization of water, leading to a reduction in the dose of coagulant applied by 27%.