D.C. Mun. Regs. tit. 14, r. 14-601
Minimum basic plumbing facilities in buildings used in whole or in part to house one (1) or more habitations shall be as required in this section, except as specifically provided otherwise in § 602.
Each dwelling unit, except a bachelor apartment, shall contain a kitchen sink for the exclusive use of the occupant(s) of that dwelling unit.
Each dwelling unit and each rooming unit shall have available for the use of the occupant(s) of that unit a lavatory, a water closet, and a bathing facility.
Each kitchen sink, lavatory, and bathing facility required by this chapter shall be properly connected with both hot and cold water lines.
All plumbing fixtures shall be properly connected to the public water system and to an approved sewerage system.
Any lavatory required to be installed by this subtitle shall be located in the room or compartment with the required water closet, or as close to it as practicable, except as provided in § 601.7
If a lavatory is not provided in the same room with the water closet, the specific location of the lavatory shall be approved by the director.
D.C. Mun. Regs. tit. 14, r. 14-601