A small amount of solvent can make water unfit for drinking. Treatment systems to remove these contaminants can cost thousands of dollars. Used thinners and reducers from paint preparation, mixing and clean-up are typically hazardous wastes due to ignitability or toxicity, or because they are identified on the RCRA lists of hazardous waste. Because they are hazardous, they must be recycled or disposed of as a hazardous waste. This means they cannot be simply left to evaporate or disposed of at a landfill or resource recovery facility.
Recycling is a preferable solution for waste solvents.
As a last resort they may be disposed of at a permitted hazardous waste facility using a permitted hazardous waste transporter. Using Solvents Reduce Use only the minimum amount of solvent recommended. For example, scrape paint cups with a plastic spatula before rinsing with solvent. Use Teflon lined metal paint cups to make cleaning easier and reduce solvent need. Prevent evaporation by using tight fitting lids or stoppers.