Lav A no water supply (BBJ)

[flyday]

Hi,
after few hours in air, the water supply to Lav A stopped. No water to faucet nor to toilet flush.
tried to set Lav A water supply & SOV to different positions, no help.
There is no signs of water leak as water quantity does not drop irregularly.
***This is BBJ model, the water manifold supply water to Lav A, galley, guest lav. Only Lav A has problem.

Is it possible water supply & SOV failed in CLOSE position?

Any thoughts, guys?

Thanks,

[sjap]

Is the problem still present?
Do you have any water pressure at other locations? Just to make sure the pressurization of the tank is ok.
If present, i suggest to loosen the water connection slightly at the coupling near the lav where it comes from the water tank to see if the pressure reaches the fromnt of the plane.
Normal 737 have the water supply line running above the ceiling panels to the galleys etc. (al least i know of of th fwd RH galley where the supply is above the front galley ceiling)
try to acces the supply line and from there start troubleshootinh towards the failed components

[maro12]

Hi Flyday,

Do You have Cabin Outfitting Manuals (AMM Supplement, IPCS, etc.)? Do You know which outfitting center done the cabin? Can You share this info? BBJ1,2 or 3?

How Galley and Guest Lav You mentioned are situated in the cabin?

Dependent on outfitting center water system might be modified in many ways on BBJ, including for example IR SOV, extra filters etc. but if You have original Boeing Lav A module, I would guess water sys was not changed so much there.

I would find AMMS (You should have it with Your documentation) and see how system looks and what is on the way which could fail.

Water line is in the ceiling like Sjap mentioned (BBJ usually no difference up to the modules, but than in the Lav module might be different things) and if You have water pressure in Fwd Galley (You did not say that galley is in front, I assumed it, correct me if I am wrong) I would think that pressure is ok.

Best Regards,
Maro12

[flyday]

Thanks for reply.
Yes, it is original Boeing Lav A.
Nothing wrong on the other galley, lav. pressure, water flow.
Only Lav A has problem.
On the ground, the problem still there.

Will anyone have water supply & SOV CMM?
I am going to try to remove the SOV and check the flow.
Any other idea?

I have attached the layout of the water/waste diagram for ref.

[maro12]

Hi Flyday,

It looks pretty straightforward. First logical step would be to check if water ok on the input to SOV (maybe try to bypass it for test).

I had a case with complaint with a low flow to one of the Lavs after several hours of flight with request to check heating elements on the water hoses (on this particular ac all water hoses in cabin had heating elements controlled by built-in thermostats, like standard Boeing hoses in waste tank area). One of the ideas was that water in the line might freeze up after several hours in the air in certain conditions, and with heating elements/thermostat faulty. But after check heating elements/thermostat found to be ok, and after further discussions we found this probable cause rather unlikely. Unfortunately I do not know if and how the problem was fixed at the end.

Let us know.

Best Regards,
Maro12

[flyday]

Thanks Maro12.
Ya, looking at schematic, fairly simple system.

As the supply&SOV is a pure mechanically operated valve, that is why I am wondering if the SOV is the cause, ie failed in close position(supply off) in a sudden.
If not, I am out of idea why.
In this case, seems water supply tube doe NOT have heating element. And it is NO flow not low flow.

That is why asking for CMM.

[maro12]

Hi Flyday,

I see Your point, I would look for CMM also, unfortunately no access now.

I also agree that probability that this valve failed closed itself from open position is very low (manually operated 4 way valve), but still this is the easiest step to check at this moment and worth to see if You have water into the valve. You mentioned that You were trying to move the SOV valve in different positions, and if this did not change anything, even less likely there is water in.

If not, than we look further.

Is Fwd galley at aprox same station as Lav A (in front of P6 back wall) or further back?

If is is on same sta, I would say pressure is ok, but still needs to be checked, as I might be wrong of course. To check it You would need to remove ceiling panels: cockpit entry and/or above fwd entry and check for water presence there in line somehow like Sjap mentioned, although couplings might be installed on hoses joints, which I think can not be just slightly loosened, and You would not like trying to remove it with water pressure - I am not sure if You can loosen it, maybe Sjap could tell more on that one.
On many BBJs Fwd entry panel is definitely not one man job - the one You need to remove to replace battery packs if no quick access provided, very big and You need to remove some parts from Lav A wall also - but depends on configuration, I do not know which cabin You have.

Did You do any major maintenance which required access and Lav A/Fwd Galley removal lately?

Did You see if water is coming out from fwd drain port? (I am thinking what would happen if drain valve started to leak through, although low probability also I would think)

Best Regards,
Maro12

[maro12]

Good Day Flyday,

It is also worth to go through FIM 38-10 Task 803 to check all items which could degrade water system pressurisation like:
-check fill/overflow vlv for air leak,
-press relief valve,
-check valves,
-filters,
etc.

Also to access a little more Lav A supply line, removal of oxygen box would be an option.

Best Regards,
Maro12

[flyday]

SOV removed and checked serviceable.
Now water supply seems back to normal without any part replacement.
****I should check water flow BEFORE SOV remove/install (possible air lock?)

The Lav A is right FWD of Door 1L at STA 290 apprize, while Lav Guess is right AFT of Door 1L at STA400
Galley is then right after Lav Guess at STA 490.
***Refer to water tap point

Now seems problem pointing to icing/frozen tube?
But I have no clue why as Lav Guess & Galley work normal.

Will need to wait another 10+ flight to see if problem comes back.

[maro12]

I would rather point towards water system pressurisation.

On BBJs it would be even more difficult to cause line to freeze, as they in most cases have additional soundproofing which makes another layer of thermal insulation. Boeing lists it as probable cause, but I would say it would most likely happen on ground in cold weather without air conditioning running, in flight in my opinion probability of that happening is very low.

From what You wrote, Lav A is most forward situated water tap point, therefore it is possible that in case of water pressurisation system decreased performance, in certain conditions water would not get there. The causes might include air leaks in tank pressurisation system as well as restricted water flow in water lines.

It is just my guess.

Could You confirm if the issue was also there when water tanks were completely full?

Best Regards,
Maro12

[700Ctech]

I would guess the water supply line is sitting next to the skin and freezing. I have seen this happen on ours after long flights. There may be insufficient insulation at that location.

[flyday]

I would rather point towards water system pressurisation.

Could You confirm if the issue was also there when water tanks were completely full?

Best Regards,
Maro12

Problem does not exist when tank is full.

[flyday]

I would guess the water supply line is sitting next to the skin and freezing. I have seen this happen on ours after long flights. There may be insufficient insulation at that location.

Thanks for input. That would be a case, but remotely possible as for Lav A where MEC close-by?

[flyday]

Quick update:
Recently in 2 more than 7 hours flights, problem does not exist.

So far, no positive finding, no part replaced.

No more problem.

[maro12]

Hi Flyday,

Thank You for feedback.

Did You notice any anomalies in compressor operation, when no bleed air (I mean time and frequency of activation)?

I do not see Your drawings anymore, but I am assuming water pressure cut-out switch is still there on modified system (placement of this switch might also be important). Considering only compressor line at this moment (no bleed), I would think that if this part of the line would not keep the pressure: 1. it would take longer for compressor to pressurise the tanks, 2. compressor would run more frequently. And as this line have a common section with bleed, You verify this part of the line at the same time.

Just an idea, maybe worth to do some observation there. It is easy, and might give some clues.

Also, can You confirm that after affected flights, after landing on ground problem still existed? (situation before You serviced tanks and after).

My reasoning:
-if it was freezing line, after You landed (assuming place with temperatures above 0deg C), left aircraft let us say overnight, or even keep packs on for a while, system should start to work even with little water in tanks;
-when tanks are full there is also hydrostatic pressure in the equation which helps to push water out, therefore if tanks are low and air pressure is slight below limit required to get water to LAV A You might face described situation. Additionally if there are any flow restrictions (other than ice if applicable, kinks for example) also matters. I never done design calculations on the system and I am not sure how significant are those dependencies, but I would say that is something to keep in mind.

@700Ctech,

I would guess the water supply line is sitting next to the skin and freezing. I have seen this happen on ours after long flights.

How did You confirm that freezing was actually the case?

Best Regards,
Maro12

[flyday]

Hi Flyday,
Did You notice any anomalies in compressor operation, when no bleed air (I mean time and frequency of activation)?
Also, can You confirm that after affected flights, after landing on ground problem still existed? (situation before You serviced tanks and after).
Maro12

Hi Maro12,
did not chk compressor ops. seems ok?
on that flight, problem was still there after landing, even 30 minutes later.

We recently had a 11 hours flight, no problem at all.

[maro12]

Hi Flyday,

Let me recap (correct me if I am wrong):

-Problem started in flight after several hours, water level was running low,

-After landing, even 30 min on ground, problem continues (before water servicing).

Next questions I would ask:

When exactly problem went away?

Was it after water servicing?

Was it after any specific action on the aircraft/system?

Did You notice exact water level when problem appeared?

Did You go as low as during affected flight in water level during recent flights?

Let's observe.

Best Regards,
Maro12

[flyday]

Hi Flyday,

Let me recap (correct me if I am wrong):

-Problem started in flight after several hours, water level was running low,
--------water level does NOT run low, it is no water goes to Lav A faucet and Rinse valve

-After landing, even 30 min on ground, problem continues (before water servicing).
---------correct for problem, but is not correlated to water level.(more than half full of tank)

Next questions I would ask:

When exactly problem went away?
--------some days later when we back to aircraft

Was it after water servicing?
--------no

Was it after any specific action on the aircraft/system?
--------no idea. As I disconnect/reconnect the fittings to water supply SOV

Did You notice exact water level when problem appeared?
-------Water tank more than half in flight

Did You go as low as during affected flight in water level during recent flights?
-------not correlated. but we did some flights which water tank runs down to 1/3 to 1/4 full

Let's observe.
------so far, never happen again

Best Regards,
Maro12