Fresh water tank vent?

[jjpoppy]

Hi can anyone help please.

The fresh water tank on my Ocean is not venting.

After using the pump when I remove the filler cap I can hear the air pressure equalising.

Van is out of warranty period so its down to me!

Where is the vent tube? can I get to it to clear it? Would a small hole drilled through the inner part of the filler cap work?

Regards in anticipation of assistance.

 

[WelshGas]

Hi can anyone help please.

The fresh water tank on my Ocean is not venting.

After using the pump when I remove the filler cap I can hear the air pressure equalising.

Van is out of warranty period so its down to me!

Where is the vent tube? can I get to it to clear it? Would a small hole drilled through the inner part of the filler cap work?

Regards in anticipation of assistance.

This might help.

 

[Roger Boeken]

I experienced the same on new delivered 6.1. Filled kitchen sink several times in a row to flush the system and i noticed pressure getting lower each time. When I tried to open filler cap there was a strong vacuum inside. If 17-34-22 is the overflow/vent , how can it be inspected for proper working ?

 

[WelshGas]

I experienced the same on new delivered 6.1. Filled kitchen sink several times in a row to flush the system and i noticed pressure getting lower each time. When I tried to open filler cap there was a strong vacuum inside. If 17-34-22 is the overflow/vent , how can it be inspected for proper working ?

I presume the vent would open into the water inlet somewhere. Probably covered by the lockable cap.

 

[Resfeber]

Think this also shows tank vent location
Post #6 in thread 'Fresh water tank vent'

Fresh water tank vent

Hi all, just getting to grips with the new Ocean and todays task was sterilise the water system and flush it out, so I dropped in a couple of sterilising tabs, filled up the tank, waited 20 mins and then flicked on the tap and started to run it through. All was working fine until I heard a...

vwcaliforniaclub.com

 

[Johnny Rocket]

Take the finisher panel out behind the sliding ‘triple-shelf’ blind thing in the NSR quarter (3x 2-part plastic fasteners released with a ca. 3mm Allen key) and you will be able to see down to the filler neck and the vent pipe - I spotted that mine had a bit of a pinch in it although it doesn’t prevent the vent. Yours may be different?

(the vent tube is item no. 34 in the exploded diagram above I think)


UPDATE 18-AUG-22:

I had to go back into this area today to tidy something up, so I took a couple of photos to help anyone trying to trace such a problem in future - the tank breather is the white hose to the right of the convoluted grey/white 'donkey dick' filler hose, going from the (lower) yellow fitting on the tank (up) to the backside of the water tank filler cap receptacle. I guess that the cap functioning properly and as designed is key to the system correctly venting, hence, I presume, the success with drilling the 2mm hole?

 

[jjpoppy]

Thank you to all, who came to assist.

Following careful examination of the exploded parts diagram, and examination of my van filler, vent pipe, and filler cap I came to the conclusion the vent pipe feeds into the filler pipe just inside the cap, so it needs to vent through the cap.
I drilled a 2mm hole into the centre of the white plastic 'bung' part of my cap - hey presto problem solved, tank vents. I can now drain the tank with cap on, and Ill be able to drive up into the Alps again not worrying what is happening to my water tank.

 

[jjpoppy]

Take the finisher panel out behind the sliding ‘triple-shelf’ blind thing in the NSR quarter (3x 2-part plastic fasteners released with a ca. 3mm Allen key) and you will be able to see down to the filler neck and the vent pipe - I spotted that mine had a bit of a pinch in it although it doesn’t prevent the vent. Yours may be different?

(the vent tube is item no. 34 in the exploded diagram above I think)


UPDATE 18-AUG-22:

I had to go back into this area today to tidy something up, so I took a couple of photos to help anyone trying to trace such a problem in future - the tank breather is the white hose to the right of the convoluted grey/white 'donkey dick' filler hose, going from the (lower) yellow fitting on the tank (up) to the backside of the water tank filler cap receptacle. I guess that the cap functioning properly and as designed is key to the system correctly venting, hence, I presume, the success with drilling the 2mm hole?

View attachment 98030View attachment 98029

Hi Thanks for the photos, they confirm my thinking that the breather pipe fed into the filler hose mounting, and that for the breather to work it has to be through the actual cap, which seals onto a rubber gasket when secured - not sure what the VW resolution would have been, probably a new filler cap, but the 2mm hole seems to do the trick, and it was easy to do as there was already a 3mm indentation in the centre of the bung so I just carefully drilled through the white plastic.

 

[Resfeber]

Hi Thanks for the photos, they confirm my thinking that the breather pipe fed into the filler hose mounting, and that for the breather to work it has to be through the actual cap, which seals onto a rubber gasket when secured - not sure what the VW resolution would have been, probably a new filler cap, but the 2mm hole seems to do the trick, and it was easy to do as there was already a 3mm indentation in the centre of the bung so I just carefully drilled through the white plastic.

Be interested to see how this plays out over time re any water quality issues.
It also begs the question why VW did not go down the route of a non return valve direct to atmosphere unless the breather pipe is to also cope with expansion of the air above the water if the tank gets hot as well as admitting air to stop the vacuum developed when the pump removes water.

Number of people have commented on improved tank emptying by removing cap to prevent a vacuum developing but cannot find anything about tap discharging water without the pump in hot Weather, even when the tank water becomes tepid.

 

[WelshGas]

Be interested to see how this plays out over time re any water quality issues.
It also begs the question why VW did not go down the route of a non return valve direct to atmosphere unless the breather pipe is to also cope with expansion of the air above the water if the tank gets hot as well as admitting air to stop the vacuum developed when the pump removes water.

Number of people have commented on improved tank emptying by removing cap to prevent a vacuum developing but cannot find anything about tap discharging water without the pump in hot Weather, even when the tank water becomes tepid.

Possibly because the water tank system must cope with changes in atmospheric pressure, altitude and temperature.
As water expands with a rise in temperature so, probably, does the plastic tank.

 

[Johnny Rocket]

For anyone interested, but perhaps still confused (and sorry, no intention at all here to patronise!):

A breather is nothing more than a small-bore atmospheric vent tube fitted high up / at the top of a liquid vessel, if possible in a position where there isn't normally expected to be much slosh, and even so it is then often made long and / or convoluted, so that spillage overboard is minimised.

The system needs to equalise internal tank pressure (due to filling, emptying, atmospheric changes, thermal expansion, etc., etc.), and, crucially, it must always work in whichever direction the imbalance is - thus it must accept a balancing air flow in either direction. In which case you'd need to employ two opposing one-way valves, at which point the device collapses back and is equivalent to just a simple breather.

By contrast, your vehicle fuel tank, due to modern evaporative emissions regulations, has to have something FAR more elaborate, where a balancing flow of air must be allowed in as fuel level drops, but vapour must never be lost, say due to a rise in ambient temperature and consequent rise in pressure of the volatiles (= vapour) above the liquid fuel, since fuel fumes (unlike liquid water or water vapour!) represent both a fire risk and an atmospheric pollutant.

 

[jjpoppy]

Some good points raised, thank you all.
I did consider the possibility of contamination into the water tank through drilling a hole in the cap, but decided on balance there was more likelihood of contamination on filling if not careful than through the 2 mm hole, (I always try and use my own hose to fill!).On balance I considered the possible damage to the tank, pipe, or pump with a tank clearly not venting more likely and potentially more expensive than possible contamination of water in the tank which is relatively easy to resolve.

 

[SuperSeven747]

I experienced the same on new delivered 6.1. Filled kitchen sink several times in a row to flush the system and i noticed pressure getting lower each time. When I tried to open filler cap there was a strong vacuum inside. If 17-34-22 is the overflow/vent , how can it be inspected for proper working ?

Hi @Roger Boeken

Did you ever figure out how the water tank vents?

I have a brand new Cali, and after 2 sinks of water the tap pump grinds to a halt as it can no longer pump the water due to lowered pressure in the tank.

If I then remove water filler cap, I get a mightily whoosh noise as air rushes into the tank to equalise the pressure.

There must be some way air should be being pulled in as water is drawn out?

 

[Johnny Rocket]

I would imagine that either the breather air path through the cap isn't open as it should be (someone with the same issue, in this or a similar thread, drilled a 1mm hole in the cap I recall), OR the white small-bore hose providing the pressure-equalising pathway from the tank is pinched - see photos I put up in my post of 15/18-Aug-22 above.

 

[Roger Boeken]

Hi @Roger Boeken

Did you ever figure out how the water tank vents?

I have a brand new Cali, and after 2 sinks of water the tap pump grinds to a halt as it can no longer pump the water due to lowered pressure in the tank.

If I then remove water filler cap, I get a mightily whoosh noise as air rushes into the tank to equalise the pressure.

There must be some way air should be being pulled in as water is drawn out?

No I did not figure out. But some theories I have:
1.we are not supposed to fill several sinks in a row. Normal usage like filling water kettle does not give any problems. A short wait is enough to release the vacuum.
2. vents are possible source of contamination, I would never drill a hole in filling cap as some suggest..
3. this vacuum may have a positive side effect : water in the pipe between tank and tap is partially sucked back to the tank . Water staying for a long time in the pipe between pump and tap is more subject to bacteria growth I think. But maybe this is just wishfull thinking..
4. If I intend to flush the water system or empty the water tank I open the filling cap without removing it completely to allow venting.

 

[WelshGas]

No I did not figure out. But some theories I have:
1.we are not supposed to fill several sinks in a row. Normal usage like filling water kettle does not give any problems. A short wait is enough to release the vacuum.
2. vents are possible source of contamination, I would never drill a hole in filling cap as some suggest..
3. this vacuum may have a positive side effect : water in the pipe between tank and tap is partially sucked back to the tank . Water staying for a long time in the pipe between pump and tap is more subject to bacteria growth I think. But maybe this is just wishfull thinking..
4. If I intend to flush the water system or empty the water tank I open the filling cap without removing it completely to allow venting.

I’m sorry but I think you are over thinking things.
The fact that an air- vent tube is fitted alongside the large bore filler tube is surely evidence that it vents to the outside, somewhere within the filler/cap system.

The above photo by @Johnny Rocket shows the inlet tube opening into the filler body ,presumably to the side of the shelf that the rubber seal on the cap seals to.
The failure to vent is probably down to a number of possible causes.
1. Oversized rubber seal on locking cap.
2. Malposition of the rubber seal.
3. Obstruction of the vent orifice.

 

[Roger Boeken]

I’m sorry but I think you are over thinking things.
The fact that an air- vent tube is fitted alongside the large bore filler tube is surely evidence that it vents to the outside, somewhere within the filler/cap system.

The above photo by @Johnny Rocket shows the inlet tube opening into the filler body ,presumably to the side of the shelf that the rubber seal on the cap seals to.
The failure to vent is probably down to a number of possible causes.
1. Oversized rubber seal on locking cap.
2. Malposition of the rubber seal.
3. Obstruction of the vent orifice.

View attachment 106814

I do not deny there is venting provided by vw and I may be overthinking but nevertheless the venting provided is not enough if you open the tap longer periods and vacuum is building up in the tank. Do you never experience this, nomatter how long you open the tap ? Then I will investigate further what is wrong in my cali. The same happens when you try to empty the tank trough the valve in the bottom, it halts after a minute if you do not open filler cap because of vacuum building up.

 

[Johnny Rocket]

I am sure that yours simply has an issue - a fault with the cap, or the vent pipe, or the mating of cap-to-receptacle.

Water should run freely from the sink tap until the tank is empty - mine does; in fact that’s how I first emptied the tank until I found the dump valve lever in the rear cupboard!

 

[WelshGas]

I do not deny there is venting provided by vw and I may be overthinking but nevertheless the venting provided is not enough if you open the tap longer periods and vacuum is building up in the tank. Do you never experience this, nomatter how long you open the tap ? Then I will investigate further what is wrong in my cali. The same happens when you try to empty the tank trough the valve in the bottom, it halts after a minute if you do not open filler cap because of vacuum building up.

I don't have this problem at all. I can empty the whole tank via the tap & sink in one go with no change in flow, likewise draining the tank I do not have to remove the cap.
Although mine is an older vehicle the water tank system is the same including Part Numbers.
So I believe something is obstructing the correct operation of the venting system in your case.

 

[ArunAlec]

Noticed the other day that my filler cap has a very small hole in centre of the inner part, which vents through the lock. This would function as a vent when taps are on.
I wonder if the large vent that comes from the tank to the “wrong“ side of the cap seal is just to allow air out of the tank when filling, to prevent “splash back” up the filler.

 

[Johnny Rocket]

Noticed the other day that my filler cap has a very small hole in centre of the inner part, which vents through the lock. This would function as a vent when taps are on.
I wonder if the large vent that comes from the tank to the “wrong“ side of the cap seal is just to allow air out of the tank when filling, to prevent “splash back” up the filler.

You're of course right - the vent pipe in my photo appears WITHIN the sealing face diameter for the cap on the receptacle, so it is indeed an anti-glug vent for tank filling, whilst pressure-balancing when the cap's on and water is consumed, etc., is achieved via the small hole in the centre of the cap.
I tried sucking and blowing through mine earlier, with the inner cap body part both extended and then compressed (the latter the state when the cap is fitted), and couldn't get any flow, but this is certainly the air path - I'll investigate some more later and report! . . .

18:30 UPDATE

OK, so for the hell of it I took my cap apart today - see picture sequence below:

The little indent you see in the centre of the smaller-diameter part of the single piece white plastic 'top-hat' body is NOT a through-hole (on the reverse side view you see a blob of pink grease to lubricate the spring seat, but there is NO perforation here), and given that the water tank cap black rubber (washer) seal sits on the top face of the 'brim' of this top hat, then there appears to be no air path at all (at least via the cap assembly) from the filler neck of the tank past this top-hat body, and then out to atmosphere!

The final photo shows the filling anti-glug vent described by AA above.

So, I'm afraid to say that I now don't know where the tank-to-atmosphere pressure balance occurs, but the fact remains that with exactly this set-up, as mentioned earlier, I can happily (as can WG too) drain the tank via the sink tap with the filler cap firmly on and with no loss of flowrate as the level drops to empty.

I think we've set a hare running now . . . . !

 

[Roger Boeken]

I am sure that yours simply has an issue - a fault with the cap, or the vent pipe, or the mating of cap-to-receptacle.

Water should run freely from the sink tap until the tank is empty - mine does; in fact that’s how I first emptied the tank until I found the dump valve lever in the rear cupboard!

I’m sorry but I think you are over thinking things.
The fact that an air- vent tube is fitted alongside the large bore filler tube is surely evidence that it vents to the outside, somewhere within the filler/cap system.

The above photo by @Johnny Rocket shows the inlet tube opening into the filler body ,presumably to the side of the shelf that the rubber seal on the cap seals to.
The failure to vent is probably down to a number of possible causes.
1. Oversized rubber seal on locking cap.
2. Malposition of the rubber seal.
3. Obstruction of the vent orifice.

View attachment 106814

there is no obstruction of the venting pipe to the filler pipe, looks like the filler cap is blocking the venting hole ? Still not convinced to drill a hole in the filler cap though.

 

[jjpoppy]

Well I drilled a 2mm hole through the inside of the cap (in the centre where the indent is) - that solved all my problems of the tank not venting.

I should add that not allowing the tank to vent caused problems with pumping water from the tank, draining the tank, but more important prevented the tank equalising pressure when the external air pressure changes ie driving in the Alpes. - This I considered could have caused damage to the tank.

I have not noticed any detrimental effects of drilling the hole.

It was in my opinion a gamble worth taking with the potential expense of a replacement filler cap if it went wrong. The gamble paid off, and I share my experience with others.

If the tank cannot vent there is the potential for damage to parts that are either expensive, or difficult to get to to repair/replace.

 

[Johnny Rocket]

I'm off to the dealer this morning to pick up some injector spill line clips for my daughter's Caddy - just for a laugh I'll see if I can find a mechanic who knows how the water tank pressure is supposed to equalise with atmospheric when, say, water is being drawn - don't hold your breath though . . . !

 

[dspuk]

For kicks I took my cap off and tried to suck air in and out the hole, to puzzeled looks from neighbours. No dice, but we also have zero issues with water blocks on our tank - works as intended.