Cooling water is needed as a coolant in all Pyrolysis Plastic Plant Production Units. Cooling water supplied from the Cooling Tower (T - 301) is used to supply the cooling water needs at the plastic pyrolysis plant. The process begins with water temperature 39-41℃ going into the cooling tower at the top of the tower. The water then fall into the basin in the form of rain drops. Water will come into contact with the outside air that is sucked by the fan located at the top of the cooling tower, the air enters through the cooling tower fins. The contact resulted in a decrease in water temperature to ±30℃. There is some water that comes out due to drift loose on the side of the tower and vapor loose on the top of the tower. In addition, there is also a blow down water flow which functions to release water if the water in the basin does not meet the requirements and is forced to be disposed of. This lack of water will be replaced by makeup water using Raw Clarified Water (RCW). In cooling towers, water contained in the basin must be maintained to meet the requirements. One effort to maintain the quality of cooling water is to drain it on the side stream filter containing carbon and gravel. The function of the side stream filter is to reduce turbidity in cooling water. In the plastic waste pyrolysis plant, the cooling water treatment uses the Open Circulating Cooling Water System, where the water absorbs heat through the heat exchanger until the water temperature rises. The water is then cooled again in the Cooling Tower using air. Some water will evaporate during the cooling process.