Chilled water (CHW) systems are cooling systems that circulate CHW. CHW piping; Either condenser water (CW) piping (for a water-cooled system) or refrigerant based piping (for an air-cooled or evaporative-cooled. Selection Based on Frictional Loss of 4 ft of Water / 100 ft (Pipe dia ≤ 4 inches). Pipe flow resistance from mains. Chw Piping Specs - Free download as Excel Spreadsheet (.