Point sources are generally divided into two types ­ industrial and municipal. Under the NPDES program, industrial point sources, which include commercial and manufacturing facilities discharging wastewater directly into a receiving stream, are required to be covered by a permit which specifies monitoring and reporting provisions and establishes limits on the pollutants that are discharged. If an automotive service/repair shop discharges wastewater directly from its facility (such as from a holding pond) to waters of the United States, that shop is considered an industrial point source and is subject to NPDES regulations. Wastewater (domestic wastes from households and indirect discharges of industrial wastes from manufacturing and commercial activities) discharged into rivers or streams from municipal sources (also known as publicly owned treatment works (POTWs)), are governed by the NPDES program, as well. Storm water from municipal separate storm water sewers and storm water associated with industrial activity, including automotive service/repair shops, are also considered point source discharges and are addressed by the NDPES program.

In the Automotive Service industry, most facilities discharge their water (sewage, floor drain contents, etc.) into the public sewer system. Industrial wastes entering municipal wastewater treatment plants from commercial and manufacturing facilities are regulated under the Clean Water Act by the pretreatment program, which may require such industries to pretreat their wastes to prevent damage to the collection system, interference with the operation of the plant, pass through of pollutants from the plant into receiving waters, or threats to worker health and safety. Actual limits on the amount of industrial pollutants discharged into municipal wastewater treatment plants are determined by three types of standards that apply to industry: 1) prohibited discharge standards, which include general and specific prohibitions; 2) national categorical standards, which were developed by EPA and set industry-specific limits; and 3) local limits, which are developed by POTWs to address Federal standards as well as State and local regulations.