Primary source for the potable/wash water system (PWS)?

• A. Groundwater supply
• B. Onboard water tank
• C. Condensed humidity
• D. Bleed air regulated to 30 PSI

Answer: (D)

Water systems on an aircraft need a pressure source to push water from tanks to galley and lavatory outlets. The energy that drives the potable/wash water system is provided by bleed air, regulated to a specific pressure (about 30 psi in many configurations). This bleed air powers a pump or regulator that pressurizes the water lines, enabling water to flow to faucets and wash stations. Water stored in onboard tanks or supplied from the ground ( hydrants or service carts ) are sources of the water itself, not the mechanism that moves it. Condensed humidity isn’t the primary, reliable source for full-time operation, so it isn’t considered the primary source. Therefore, bleed air regulated to 30 psi is the driving source that makes the system deliver water.