N.Y.C. Admin. Code § 24-519: § 24-519 Volatile, flammable liquids.

It shall be unlawful to use any connection with, opening into, or gutter leading into, any sewer or drain, either public or private, for the conveyance or discharge, directly or indirectly, into such sewer or drain, of any volatile flammable liquid, gas or vapor. A volatile, flammable liquid is any liquid that will emit a flammable vapor at a temperature specified in rules of the department.