Airplane General - Potable Water
The following notes are from the Maintenance Manual
The potable water system has a single water tank which stores and supplies fresh water to the galley units and lavatory wash basins.
757-300: The potable water is also supplied to the lavatory toilets for use in the water flush cycle
The potable water tank is in the compartment aft of the bulk cargo compartment and has a capacity of 60 gallons (757-300 - 120 gallons).
Each galley and lavatory has water shutoff valves above the floor, allowing any one unit or combination of units, to be isolated while the rest of the units remain operating. Each lavatory has a water heater in the supply line to the wash basin faucet.
Potable water quantity indicators at door R1 and at the ground servicing panel show ground service personnel and the flight crew how much water is in the potable water tank.
The potable water tank is pressurised to force water from the tank to the lavatories and galleys. The pressurisation system utilises a Potable Water air compressor, augmented by bleed air from the Left pneumatic system.
