This manual describes typical ‘best practices’ and strategies used in petroleum refineries to manage water, including ways to reduce water usage. Improved water management in a petroleum refinery can potentially reduce the volume and cost of raw water used in refinery operations. Furthermore, improved water management may result in reductions in wastewater flow or contaminant load or both. Lower flow and contaminant load may result in lower wastewater treatment operating and maintenance costs. Optimized water management may also reduce the mass of contaminants in the treated effluent, thus improving the quality of a wastewater discharge and ultimately the environmental impact of a refinery’s discharge.