Abstract: Electrolytic probe adapted for use in a heat transfer system, to ground the positive electrolyte of the water in the heat transfer system, and thereby prevent lime formation, scaling, pitting and corrosion, without the use of chemicals heretofore required to do this. The probe is supported to extend along the flow of water by a teflon seal threaded on the outer end thereof, and threaded within a fitting, threaded in a fitting secured to the inlet for the flow of water to perform its heat transfer operation. The means on the seal accommodating it to be threaded in the fitting are cut off after assembly, to preserve the seal between the probe and fitting.