It is a common problem that the cooling water loop in an HVAC or refrigeration plant is suffering from scaling, corrosion, and bacteria attacks, especially in an open-loop designs. The reason is that, through the open water loop, various kinds of contaminants were trapped and migrated along the water flow, causing condenser scaling, which in turn, leading to its poor thermal performances. The experiment conducted in this study revealed that each condenser temperature increase of 1 ¢J, accounts for a COP decrease of 2.4% to 2.8%.Serious scaling problem might even lead to system malfunction, and hazardous environmental problems. Conventionally, water-treatment in the condenser cooling water loop can be categorized into two parts, namely, the chemical and the physical methods. The chemical treatment is mainly performed by injecting chemicals, mostly acids, into the water loop so that it can circulate through the system and causing scales to peer off from the condenser tubes. In response to the cry of environmental protection, physical treatment has become increasingly important, which utilizes magnetic forces as the primary working principle. The main theme of this study is to validate this principle by full-scale experiments. The Zeta Rod system has been developed under the DLVO theory, with significant performance and is environmentally friendly. Experimental investigation has been performed in comparing the temperature differentials across a condenser, before and after the treatment. The result validated that it has increased from 3.9¢J to 4.2¢J and enhanced the thermal performances of the condenser accordingly.