Adequate sanitary toilet facilities should be provided on
board. The facilities should be at least one water closet, one shower
for every 8 persons or part thereof, and one wash basin for every
6 persons or part thereof.
In vessels where a sanitary system, including a holding tank,
is provided, care should be taken to ensure that there is no possibility
of fumes from the tank finding their way back to a toilet, should
the water seal at the toilet be broken.