Dieter Scholz (2020)
Water Contamination on Aircraft
See for figures:
Dieter Scholz: "Aircraft Cabin Air & Water Contamination/Quality – An Aircraft Systems Engineering Perspective",
Presentation, QCAQE – Global Cabin Air Quality Executive, 7th Annual Forum, London, 31 March – 2 April, 2014. -
https://purl.org/cabinair/AirAndWater (PDF, 32 MB)
1) Potential Contamination of Potable Water with Contaminants in the Bleed Air
slide 32: Water pressurization system A340 --- water tanks is connected with bleed air (compressor as alternate pressure source)
slide 33: Water pressurization system A380 --- water tanks is NOT connected with bleed air (separate compressor)
slide 34: Water pressurization system A320 --- water tanks is connected with bleed air
slide 35: Water pressurization system B737 --- water tanks is connected with bleed air
2) Potential Contamination of Potable Water with Hydraulic Fluid
Example A320 (slides 36/37)
2.1) Direct Connection of Hydraulic Fluid with Potable Water via Bleed Air Lines?
- Hydraulic reservoirs are pressurized with bleed air.
- The bleed air presses on the free surface of the hydraulic fluid and gets as such in contact with it.
- The "mixture of hydraulic fluid vapor and bleed air" is connected via bleed lines with the potable water tanks.
But flow into the potable water tanks is unlikely:
- In flight, the "mixture of hydraulic fluid vapor and bleed air" would need to flow upstream and opposite sense through two check
valves (which by design will not happen in larger quantity) to get into the bleed line for water pressurization.
- On the gound (without bleed pressure), the hydraulic fluid vapor and bleed air mixture can flow downstream(!) but would still need to flow
opposite sense through two check valves (which by design will not happen in larger quantity) to get into the bleed line for water pressurization.
2.2) Indirect Connection of Hydraulic Fluid with Potable Water via APU and Bleed Air Lines?
Hydraulic fluid leaks small amouts into the landing gear bay; from there along the bottom of the fusalage and
into the air inlet of the APU and into the bleed air - and from where a connection exists into the potable water tank.
That flow path of hydraulic fluid is visible on the fuselage (visible contamination on white painted surface).
- Contaminations of the bleed air arrive without difficulty also the potable water tanks.
- Hydraulic fluid will find its way most probably into the potable water tanks via the APU.
4) Straight Advice
Do NOT drink tea or coffee on board of an aircraft! Better safe than sorry.