49 C.F.R. § 228.317 – Toilets.

(a) Number of toilets provided. Each individual camp car that provides sleeping facilities must have one room with a functional toilet for a total of one or two occupants, and one additional room with a functional toilet if there are a total of three or four occupants.
(b) Construction of toilet rooms. Each toilet room must occupy a separate compartment with a door that latches and have walls or partitions between fixtures sufficient to assure privacy.
(c) Supplies and sanitation.
1. (1) An adequate supply of toilet paper must be provided in each toilet room, unless provided to the occupants individually.
2. (2) Each toilet must be kept in a clean and sanitary condition and cleaned regularly when the camp car is being used. In the case of a non-water carriage toilet facility, it must be cleaned and changed regularly when the camp car is being used.
(d) Sewage disposal facilities.
1. (1) All sanitary sewer lines and floor drains from a camp car toilet facility must be connected to a public sewer where available and practical, unless the car is equipped with a holding tank that is emptied in a sanitary manner.
2. (2) The sewage disposal method must not endanger the health of occupants.
3. (3) For toilet facilities connected to a holding tank, the tank must be constructed in a manner that prevents vermin from entry and odors from escaping into the camp car.