What is the primary power source for the potable/wash water system (PWS)?

The primary power source for the potable/wash water system (PWS) on the CRJ550 is bleed air. In aircraft systems, bleed air is taken from the engines or auxiliary power unit (APU) and is used for various functions, including pressurizing the potable water system. This is crucial as it ensures that water can be delivered to different points within the aircraft, such as lavatories and galleys.

Choosing bleed air as the power source for the PWS is aligned with how many aircraft incorporate pneumatic systems. Engine or APU bleed air allows for efficient operation of the water system without needing dedicated electrical power or mechanical pumps, which simplifies the overall system architecture and reduces weight.

Battery power, while it can operate various electrical systems on the aircraft, is not the main source for the potable water system due to limitations in power delivery and duration. Engine power might be presumed to include bleed air, but it is more about utilizing air at specific pressure points rather than relying directly on engine mechanical power. External power is typically used to supply electrical systems while on the ground and does not play a role in the operation of the washwater system itself during flight.