There is a simple rule for determining when it is OK to put industrial wastewater into a septic system - never. You can dispose of "sanitary wastes" from ordinary lavatory use or hand washing in a septic field only if the wastewater has not been contaminated with any water from an industrial operation.

Some yards may have shallow wells or cesspools that have been used for disposal of industrial wastewater. It is now illegal to create such systems, and existing systems need to either be closed or need to have special permits to continue their operation. This fact sheet will help you check whether your existing wastewater disposal practices are in compliance with current rules.