D.C. Mun. Regs. tit. 14, r. 14-602
Each dwelling unit shall contain a lavatory, water closet, and bathing facility for the exclusive use of the occupants of that dwelling unit, except that roomers renting space within a dwelling unit shall be permitted to share the use of the water closet, lavatory and bathing facility to the extent authorized by this section.
Where the occupants of a dwelling unit and one or more rooming units share a water closet, lavatory, and bathing facilities, at least one lavatory, one water closet, and one bathing facility shall be provided for the use of each six (6) occupants of the rooming unit or units.
Where the occupants of one or more rooming units share a water closet, lavatory, and bathing facilities, at least one lavatory, one water closet, and one bathing facility shall be provided for the use of each six (6) occupants of the rooming unit or units.
For the purpose of determining the number of occupants for whom a water closet, lavatory, and bathing facilities are to be provided as required by this section, the determination shall be made on the basis of one (1) occupant for each single or 3/4 bed and two (2) occupants for each double bed in dwelling units or rooming units the occupants of which share the same water closet, lavatory, and bathing facility, except as provided in § 602.5.
The Director may accept the affidavit of the owner, licensee, or operator to establish the actual number of occupants where it is claimed that double beds are of single occupancy.
For the purpose of determining the number of water closets, lavatories, and bathing facilities to be provided for the use of the occupants of dwelling units or rooming units required to share any water closet, lavatory, or bathing facility, the number of occupants sharing the facilities shall be divided by four (4) or six (6). Any fractional part of a group of four (4) or six (6) shall be considered a full group, and the facilities shall be provided for the use of the fractional part of a group as if the occupants constituting that fractional part constitute a full group.
D.C. Mun. Regs. tit. 14, r. 14-602