By treating water electro-dynamically, lime crystals are transformed in a manner which prevents them clinging to mains piping systems. The lime particles are held in suspension and so cannot develop their normal damaging effect. This method of water treatment preserves the normal chemical composition of the water; deliming does not occur. The vital lime content which gives the water its characteristic individual taste is not removed. Lime deposits on heating rods, which require not only expensive repairs but also increased use of energy are minimized by TESL II. Furthermore, existing deposits in the piping system will be gradually reduced.