# Mohican fresh water tank.



## dally1 (Jul 1, 2010)

Hi all,
We have just had a fantastic first weeknd away in our 2007 Mohican, everything was fine apart from one thing.

First thing we did on site was to fill the water tank. I filled away until I heard water coming out of the overflow which was fine, expected this, as it was the same with our old caravan, anyway, we were with friends and we talked there for a few minutes and was surprised to see that the overflow was still running. Never mind, I then drove onto our pitch just a few yards away and got on with setting up. Anyway, the overflow was still running.

It was quite concerning as it ran for 10 minutes or so and dropped quite a lot of water, to the degree that one bloke knocked on the door to report the leak.

Once it stopped, I checked the gauge and it read 50%. I know not to take too much notice of this but it appears to be right because I ran out of fresh water before the waste tank was full. (100 ltrs Fresh, 55 ltrs waste)

I have looked underneath but with it being an Al Ko chassis there's not much to see other than 2 overflow pipes coming through the floor. Why 2 overflows?

Is it possible that there is an overflow at 50% and another at 100%, perhaps switchable in some way I have'nt found yet? I can't think of anything else.

Why would there be 2? is it possible that someone would only want as mush fresh water on board as could be dealt with in the waste tank? A wild camper perhaps.

Has anyone else come across this, is there an answer? It seems pointless to me to have a 100 litre tank that only fills to 50 litres, you views would be really appreciated.


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## rayc (Jun 3, 2008)

dally1 said:


> Hi all,
> We have just had a fantastic first weeknd away in our 2007 Mohican, everything was fine apart from one thing.
> 
> First thing we did on site was to fill the water tank. I filled away until I heard water coming out of the overflow which was fine, expected this, as it was the same with our old caravan, anyway, we were with friends and we talked there for a few minutes and was surprised to see that the overflow was still running. Never mind, I then drove onto our pitch just a few yards away and got on with setting up. Anyway, the overflow was still running.
> ...


I suspect that the water was coming from the boiler drain drown valve which has been left in the drain position, as soon as you switch the pump on the boiler starts to fill but the water goes out the drain down. Look for a lever valve somewhere close to the boiler which is directly above the tube where you saw the water coming out. Did you use the boiler for hot water over the weekend?
Can you describe your boiler drain down valve?


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## erneboy (Feb 8, 2007)

It sounds as though it is siphoning. I had two Mochicans they only had one overflow but did tend to let a lot run out. You could try rerouting the pipe so that it runs up a bit before it goes down.

A friend of mine stuck a bolt in his overflow pipe to stop the water running out, Alan.


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## erneboy (Feb 8, 2007)

Good point Ray, in mine the drain was a blue lever you pushed down. It was under the bench seat on the drivers side beside the boiler, near where they stupidly put the immersion heater switch, Alan.


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## dally1 (Jul 1, 2010)

Thanks for the replies guys. It's definitely confined to the fresh water tank, the boiler was primed ready for use and has not been drained, also the drains for the boiler are in the rear O/S corner and the fresh water overflow is pretty much dead centre, between the rear wheels.

Rerouting pipes isn't really an option as everything is concealed and is only accessed by the smallest of panels.

I'm thinking of going down the route of simply blocking this overflow, filling the tank again and seeing if the other overflow comes into play once the tank is full.

It might be a week or two before I'm able to but I'll let you know the outcome.

Cheers.


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## dally1 (Jul 1, 2010)

I've just had a reply from Auto Trail to an email I sent them regarding this problem.

They think the tank might have collapsed causing it to syphon. The cure is to fit some "T" pieces inside to reinstate it's original dimensions.
And, they'll send me the parts to do it.  Great stuff.


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## rayc (Jun 3, 2008)

dally1 said:


> I've just had a reply from Auto Trail to an email I sent them regarding this problem.
> 
> They think the tank might have collapsed causing it to syphon. The cure is to fit some "T" pieces inside to reinstate it's original dimensions.
> And, they'll send me the parts to do it.  Great stuff.


For the tank to collapse it would suggest that there was a vacuam formed inside it. For this to happen the breather would have to be blocked, as water is used then air should replace it.
Is the tank on board?


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## dally1 (Jul 1, 2010)

Hi Rayc,

I understand what your saying and I can see how this could happen. The tank is fitted in the cavity under the floor.


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## rayc (Jun 3, 2008)

dally1 said:


> Hi Rayc,
> 
> I understand what your saying and I can see how this could happen. The tank is fitted in the cavity under the floor.


My experience of water tanks is limited but I can see that for a tank to collapse a large force would be required. A normal plastic jerry can is quite difficult to stamp down flat. As it could not have been an external force in your case then it has got to be a vacuam.

If the tank had partly collapsed then I guess the overflow could have been lower than the water level so of course water would keep escaping.

Good luck but your first job it appears to me is to inspect the tank. If it has in fact collapsed then it should be obvious and I guess you will have to remove it to fit the T pieces.


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## zappy61 (May 1, 2005)

*water tank*

Hi Daly,

I think one pipe is an overflow and the other maybe a breather pipe to let air in. Check that the latter is not blocked as the collapse may be caused by a partial vacuum when water is drawn out. Another possibility is the internal baffles have collapsed or maybe omitted, these are included to prevent water moving about when travelling and I wonder if the 'T' pieces supplied are baffles. To fit the 'T' pieces I would think you will need to remove the tank not difficult but awkward if you don't have a ramp or pit so it is best to check for simple solutions first. When you have completed your work it may be useful to sterilise the tank afterwards. (see my article here)

Regards,

Graham


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## dally1 (Jul 1, 2010)

Hi all,

Just to bring this thread to a conclusion. I have good news.  

The tank is only about 5 inches deep and holds 100 litres, so it's surface area must be fairly large. The tank roof did appear to have sunk to a degree so I fitted the parts sent by Autotrail. Placing them north south east and west I was able to lift the roof.. I then drove 50 miles to a site and filled the tank, hey presto, digital read out showed 100% full and no syphoning back. Result.


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