D.C. Mun. Regs. tit. 12, r. 12-F1101
Strike Section 1101.2 in the International Plumbing Code in its entirety and insert a new Section 1101.2 into the Plumbing Code in its place to read as follows:
Disposal. All roofs, paved areas, yards, courts and courtyards shall drain into a separate storm sewer system, or a combined sewer system, or to an approved place of disposal.
Exception: When approved, storm water is permitted to be discharged from roofs, paved areas, yards, courts, courtyards, downspouts, rain barrels, cisterns or rooftop storage facilities to vegetated areas such as lawns, gardens, grassy swales or bio-retention cells on the same lot. In such instances, the storm water shall flow away from the building and shall not flow across lot lines onto adjacent lots unless it discharges into an approved shared "best management practice" as defined in 21 DCMR Chapter 5.
D.C. Mun. Regs. tit. 12, r. 12-F1101