Airbus 321/320/319 Potable Water
 

I have noted that some aircraft retain water pressure once the bleed air is turned off and some do not. Fleet mythology has a couple of explanations. Firstly that some aircraft came with an optional electric pump, secondly that some just leak the air pressure more quickly.

As far as I can see the FCOM makes no mention of an electric pump.

Are there any experts out there who know if there is an option for an electric pump and if so how can you tell the jet has one BEFORE you put soap on your hands.

This is the most important thread I have ever seen on pprune. Hate those soapy hands.

I think it's residual pressure in the system which may take longer to bleed away on some aircraft than others. I have had running water immediately after switching the bleed off, but not on a "cold" aircraft.

The electric pump myth might come from those that transfered from a 737, which (on the NG) does have an automatic pump to keep the potable water pressurized without bleed supply.

I always just thought the loss of pressure was caused by a couple of possibilities (through personal experience). One being when the potable water cap is opened for refilling causing instant pressure loss, the other just being slow pressure loss with time.

Im intrigued to know the real answers, especially with the APU police out in force around Europe. Soapy hands and tepid coffee's are a common occurence!

Having recently been involved with A350 galley plumbing certification, a couple of possibilities I can offer are:

1. There is trapped air in the system (e.g. in dead ends to steam ovens or unused connections). This air acts as a spring or pressure accumulator, thus maintaining water pressure after the normal pressure source is turned off.
2. If there are a lot of flexible hoses in the system, these tend to grow slowly when the system is pressurized for any length of time. Once the pressure source is shut off, the hoses will contract slowly, thus repressurizing the system a little.

There is no electric pump.
When the water truck arrives to service the tank, all the air pressure is lost and does not return until the APU is running.
When you turn the APU on, turn the air bleed ON, and leave the packs off for a minute. The tank pressurises much quicker.
A good A320 will keep water pressure overnight if the tank is half full. A full tank has very little air space so will decay after a while.
If the water pressure decays as soon as the APU bleed is off, then there is an air leak in the system, usually the refill valve is not completely closed. This happens most on A320, which have the water tank in the fwd freight hold, and an electrically driven refill valve. The A319 and A321 have the water tank in the rear freight hold and a manually operated valve. (The servicing panel is always at the rear)

Afraid I disagree... our "old" A320s had the electric compressor pump, running water and tea available all day :ok:

All the new ones do not, and leak (as above) in variable amounts.

I do not know if it is/was an "option", or just Airbus stopped fitting them at some point?

Totally agree with NigelOnDraft some of them has a water compressor fitted FIN No. (8MD) and activated at 25.5psi and cuts off at 27.5psi. I believe this is a customer option and not only fittedon the old A320 but on the new ones as well we have received A319 manufactured on 2011 with electric pump fitted. On dead aircraft you might have some residual pressure trapped as the guys said and it will last for few minutes

Have to agree with NigelOnDraft.. Some have a electric air compressor (Won't work if the potable door isn"t closed properly or the magnet for the sensor has "fallen" off).Potable water is pressurized by Bleed air if no compressor has been fitted.(Just down stream of the hydraulic pick off,If the water tastes a little bit "Skydrolish" then the check valve has failed.)

It's optional. If you pay it you'll have a compressor. If not - no compressor!

Good idea to do this anyway i.e. don't hit the APU with full air loading when it has only just started because that causes heat stress on the turbine. Better to switch the load on in stages, allowing a few moments between selections for stabilisation.



One day I will learn to check the tap BEFORE I put soap on my hands........:ugh: