How is the potable water system pressurized?

The potable water system on an A320 is pressurized by the pneumatic system. This system utilizes compressed air to create the necessary pressure to keep the water flowing through the pipes to the various dispensers throughout the aircraft. The pneumatic system is designed to ensure that the water is available and at the right pressure for both passenger use and lavatory facilities.

While other systems mentioned play critical roles in the operation of the aircraft, they do not serve to pressurize the potable water system. The PTU, or Power Transfer Unit, is primarily involved in transferring hydraulic power, while the hydraulic system itself operates various flight control surfaces, landing gear, and other systems but does not influence potable water pressure. Ambient air pressure differential is not an effective means of maintaining water pressure in a closed system like that of potable water on an aircraft. Thus, the pneumatic system is specifically engineered for this purpose, ensuring the water supply is always adequately pressurized.