Singapore legislation
Regulation 112
of Road Traffic (Motor Vehicles, Construction and Use) Rules
Regulation 112
Use of lavatories, etc.
No person shall cause or permit the contents of any closet, urinal, lavatory basin or sink carried by a motor vehicle or trailer or of any tank (into which such closet, urinal, lavatory basin or sink drains) to be discharged or allowed to leak on to a road.