Fresh Water Tank Vent

I have always filled my fresh water tank until it overflows out of the vent - you definitely know it is full then. Usually it then drips for a short time and then that is that.

About to go away tomorrow (it always happens then) and having filled up the water I was a bit surprised that it continued to drip for quite a while. 

A quick wriggle underneath the van showed that the water was coming from a roughly quarter inch hole about an 1 inch from the top of the tank slightly offset from the line of level sensors.

This is a bit of a daft question from someone who has had this van for over 12 years, but is this the actual tank vent as I always thought that it was in the top?

The dripping has eventually stopped when the level dropped below the hole, but I don’t remember this happening before. 

Can anyone enlighten me as to where the vent is?

Thanks as ever

Graham

I've always assumed the breather has a mesh screen to prevent insects entering the tank.  If yours' is just a hole, it suggests the breather has become detached or the hole is something else.  There has been reportage on this Forum and elsewhere that if mains water is fed into the freshwater tank until it overflows and the breather can't release the water quick enough, the tank can become over-pressurised, for which it is not designed, and cause a sensor to pop out.  It may be in your case the breather has popped out.  However, if you fill your tank with a hose poked into the filler the water should back-up through the filler and overflow there as well as the breather and so not cause the tank to over-pressurise. 

Not noticed such a hole in ours Graham but will crawl under, have a look and get back to you asap!

Thanks Caraman, what you say makes good sense. Thinking about it, for some time now I have noticed that the level readout never achieves 100% but I put it down to the van not being level or perhaps the top sensor had got limed up. So maybe this hole should have something in it possibly a right angle breather tube that ends up above the top of the tank. The hole on its own is not large enough to be the overflow so there must be another one somewhere as it never backs out of the filler.

Thanks also Mr Hog. Please don’t go crawling under at this time of the morning it is far too early! I am heading north now but will keep in touch.

Regards
Graham

No hole in mine will send some pictures but looks like you either have the breather missing 45 degree pipe left top of tank or there should be a wire coming through the little hole slightly above the sensors. Have a good trip.
David

Hi David

Great photos, you really are a gent. It does look as if I have this breather missing which would explain matters. I hope they are inserted from the outside!

We are just stopped for a quick coffee up on the top of the A66 on the Durham Cumberland border heading up to a family member who lives a bit inland up from Ullapool, but we are going to do it this time via the Outer Hebrides. 

I did try and take a photo last night, I will try and put it on another post.

Thanks very much,

Graham

Previous photo that I had was pretty naff so I refrained from posting it.

Now back from Hebrides and have cleaned the side of the tank and taken a much better snap.







I am pretty sure now that it isn’t the breather that is missing. 

Compared to yours David, I have a hole where the white wire or tubing enters the tank at the top. Nowhere do I have either of the two white wires/tubes. (Note that my sensor wires have been sealed over).

Also if you look closely at the blown up photo, there is the remnant of a bit of reinforced tape that seems to have previously been over the hole.

Can I ask you David if you still have the original in-tank Whale pump?

My theory is that some years back I had mine removed by AS and replaced with a Shurflo. The full tank sensor would not then be needed and has been removed with the entry hole taped over. Wind forward a few years and the tape gives way and gives me this leak.

My thoughts are to just seal up the hole with something better than tape unless anyone knows any better!

Thanks

Graham

Could it have been for the power cable to the Whale pump??

Try putting a fresh piece of tape over it and check that the tank still vents/overflows OK. If it does then remove the tape and put a gob of CT1 or OB1 in the hole.

Yes I still have the whale pump, I also have a Henderson TCL4 hatch in the back of the tank which gives easy (relatively) access to change the pump, vent the tank and clean the sensors.
Your explanation sounds quite feasible I would do as others have said block the hole and see what happens

Thanks Bargee and David. 

Having filled up quite a few times over the last fortnight I am confident that the overflow works fine but I agree that the temporary followed by a more permanent seal is the best way to go.

It’s a pity all tanks are not fitted with a hatch, but that is another story…..

Thanks again
Graham

Did you have a chance to get to the bottom of your tank Graham? (pardon the pun)
Filled up for departure yesterday, no reading on 75% or 100%. Hatch off, cleaned the senders, refilled and it was no better. The wiring as above had rusted where it attaches to the tank, remade all the connections with soldered U shaped ends and reattached them, then siliconed over the whole lot. That wiring is really thin and the attachment points to the senders are puny. Emptied the tank all the indicators worked, leaving it to dry hard for 24 hours then will make sure they still work on refilling!
When we get back next month I will strip the whole lot down and rebuild it properly, it certainly isn't a quality job at the moment!

Last week I fitted my new Topargee bluetooth water tank gauge (really a usage meter) and it works very well so far, although not battle tested long term. With luck that will eliminate another area of rubbish AS wiring and gimmickry. It took just minutes to install in the output line from the Shurflo and will allow me to advise my wife when she reaches the 15 litre shower limit! It tells me to the litre how much water remains in the tank, so no guessing whether we are nearly half full or nearly 3/4 empty.

https://www.amazon.com/Topargee-Bluetooth-Water-Gauge-H2F-BT12/dp/B09F2T4HWY