Aircraft Water and Waste System Overview

Toilet System Operation

• The Flush Control Unit (FCU) starts the flush sequence when the flush switch is pressed.
• The FCU opens the rinse valve and flush valve in sequence to evacuate waste material.
• The FCU sends a signal to the VSCF to operate the vacuum generator.
• The vacuum generator creates a differential pressure between the cabin and waste holding tank to move waste from the toilet bowl.

Vacuum System Operation

• Above 16,000 ft, the vacuum generator is not started by the VSCF, as the differential pressure is sufficient.
• The VSCF monitors the operation of the toilet system and sends failure data to the CFDS.
• The CFDS fault messages of the toilet system are accessible via the MCDU.

Safety Precautions

• Obey all AMM safety procedures when working on aircraft to prevent injury and damage.
• Ensure warning notices are in position before starting a task.
• Clean hands with soap and water after completing work to prevent infection.
• Do not work on the waste and portable water systems simultaneously to prevent contamination.
• Use a plastic bag to contain removed components of the toilet waste system and seal the bag before attaching documents.

Potable Water System

• The potable water system supplies water from the water tank to users through a distribution system.
• Users include water faucets in galleys and lavatories, and vacuum toilet units.
• A water heater supplies hot water to the water tap under the washbasin in each toilet unit.
• The potable water system is pressurized by the bleed air system, and optionally by a compressor on the ground.

Waste Water System

• The waste water drain system collects waste water from lavatory washbasins and galley sinks.
• Waste water is discarded outside through the drain valve and heated drain mast.
• Air stop valves avoid constant cabin depressurization by opening only when a certain amount of water is collected.

Waste Holding Tank

• Waste holding tank servicing is done from the toilet servicing panel.
• On ground and in flight below 16,000 ft, a vacuum generator is used to generate the necessary delta pressure.

Learn about the components of an aircraft water and waste system, including the potable water system, waste water system, and toilet system. Understand how water is supplied, distributed, and heated on an aircraft.