Abstract: A reliable and efficient device for the treatment of liquid system, to inhibit scale formation, subjects the liquid to an electrostatic field and includes a pair of concentric cylindrical electrodes mounted one within the other with a dielectrically isolated flow passage therebetween. The outer surface of the inner electrode and the inner surface of the outer electrode each have a layer of electrical insulation thereon to severely limit current flow to and from the liquid, and a circuit is provided for continually applying D.C. potential to the electrodes. Dielectric fluid fittings connect the device into a liquid system. The dimensions of the inner and outer electrodes and the thickness of the insulation thereon are determined, according to the parameters of the liquid system and the chemistry of the liquid, from a mathematical model of the treating device as the equivalent of three capacitors connected in series.