Abstract: An ionization chamber for use in eliminating or controlling scale in water systems, such ionization chamber including a generally cylindrical housing having a side wall and ends, and an electrode, extending within the housing along the longitudinal axis thereof, the electrode and the housing being connected to the opposite poles of a source of direct current. The electrode projects into the housing through one end wall thereof, and the extending end of the electrode is spaced from the opposite end wall of the housing by a dimension substantially equal to the radial spacing between the electrode and the side wall of the housing. A dielectric sleeve is arranged about the electrode, and extends along the electrode from the aforesaid one end wall for a length corresponding to the spacing between the end of the electrode and the opposite end wall of the housing.