Wastes may be disposed of down a drain, even if they are hazardous. Specifically, wastes that are mixed with domestic sewage and discharged to a publicly owned treatment works (POTW) are not regulated under RCRA, because they are subject to the Clean Water Act (CWA) (§261.4(a)(1)). This exclusion is commonly known as the domestic sewage exclusion and helps avoid duplicative regulation of wastewaters that are subject to the CWA (45 FR 33084, 33097; May 19, 1980). However, a hazardous waste that is accumulated, transported, or managed prior to introduction into the sewer system, would still be subject to regulation as a hazardous waste (Memo, Williams to Stringham; September 25, 1986 (RCRA Online #11181)).
A generator may discharge waste down the drain to a POTW as long as the discharge is in compliance with all applicable wastewater standards. Applicable wastewater standards typically include national pretreatment standards, state limits, and discharge limits imposed by the POTW.
Additional guidance regarding the domestic sewage exclusion is available in the following documents: