Disappearing fresh water

[Offagain]

I have another question for the technical department.
When we fill up with fresh water the read out on the master panel says 100% and water comes out of the overflow under the van. All ok so far.
After we've been driving for a while (typically a couple of hours) it shows anything between 55% and 65% having not drawn anything from it.
There doesn't seem to be a leak (no puddles and no water trails behind us) so it's a bit of a mystery. And also very annoying.
This isn't a new thing, it's been happening since we bought it in November but we though we were just using a lot of water. Until we started checking it regularly before drawing any off from the supposedly full tank.
I hope it's something blindingly obvious that we've just missed.
Any thoughts please and thanking you??

 

[Langtoftlad]

I hope it's something blindingly obvious that we've just missed.

Inaccurate water gauge?
I now use a cheap flow meter on the hose

 

[Nirvanauk]

These gauges are sooo unreliable

 

[WillH]

I have ignored our water and waste water gauges for years. Rule of thumb, if you put ten litres in the water tank roughly ten litres will end up in the waste tank. After using your van for a while you get a feel for how much water you actually use, we put ten or twenty litres a day into the water tank and take a similar amount off the waste tank or just empty it.

 

[charliesgrandad]

I always use the overflow as my water gauge ,never use the one on the control panel and as @WillH says you get a feel for what your using and to know when to top up

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[pappajohn]

It has been know for the overflow tube to be too low in the tank (lazy/distracted installer) and once full and overflowing will act as a syphon draining the tank until the end of the overlong tube is above the tanks depleted water level.
If the tube is 1/4 way down the inside of the tank then 25% of the water will be syphoned off before the level is below the tube and the syphon suction is broken.
If there's an inspection bung on top of the tank get an arm in and see if you can feel the overflow tube inside the tank.

 

[Devon Sue]

Do you drain down between trips, if the heater empties as well it can take half a tank to refill. We have been caught out by that before

 

[bigtwin]

As you drive along, accelerating and braking, there is a lot of sloshing around goes on and a lot of energy therein to expel water out any overflow.

Ian

 

[Lenny HB]

It has been know for the overflow tube to be too low in the tank (lazy/distracted installer) and once full and overflowing will act as a syphon draining the tank until the end of the overlong tube is above the tanks depleted water level.
If the tube is 1/4 way down the inside of the tank then 25% of the water will be syphoned off before the level is below the tube and the syphon suction is broken.
If there's an inspection bung on top of the tank get an arm in and see if you can feel the overflow tube inside the tank.

Agree, it could just be bad design, we had a caravan if you filled the tank after 50 miles it was only 50% full.

 

[scousebird]

Anthea our Bailey water tank is the same as yours. Unfortunately water leaks out of the overflow when you are travelling. Alan has fashioned a "plung" for ours - a cross between a plug & a bung that he pugs into the overflow when we are travelling. When we first discovered it Alan just used some shapeable ear plugs to block it until he could make his "plung".

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[gus-lopez]

What the last 3 posters have said.It will be one of them

 

[bigtwin]

What the last 3 posters have said.It will be one of them

There is another option; the OP is a very erratic driver!

Ian

 

[Duck Truck]

the water sloshes around
and some is bound to be forced out the overflow as you drive

 

[bigtwin]

As you drive along, accelerating and braking, there is a lot of sloshing around goes on and a lot of energy therein to expel water out any overflow.

Ian

the water sloshes around
and some is bound to be forced out the overflow as you drive

I like your thinking!

Ian

 

[klaatu]

Perhaps as you drive along, the water sloshes around, and can be forced out of the overflow?

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[Jim]

I agree its likely to be siphon or slosh effect via the overflow. I had it on one van so bad I put a tap on the overflow. When wildcamping and needing all the water we could get, I'd close that tap and fill my square tank so full it would look round. . If you do the same be careful.

 

[two]

Perhaps that is one of the reasons that my tank does not have an overflow?

 

[Offagain]

Thanks all.
Despite not seeing any water trails I think sloshing and leaking from the overflow is probably the answer. We'll be filling up (again) today so I'll suggest to paul that we try the bung in the overflow pipe option.

 

[Reallyretired]

I also use the overflow as a guage when filling and do lose a bit when driving, not a lot in my case.

 

[Allanm]

Is the water emptying itself out or is the gauge faulty?
To find out which is the problem, fill the tank till it overflows, go for a drive then stop and try and fill it again till it overflows.
If you have to put more in, the overflow may be letting water out (or there may be a leak somewhere else.)
If you can’t get anymore in, the gauge is at fault.

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[Offagain]

Is the water emptying itself out or is the gauge faulty?
To find out which is the problem, fill the tank till it overflows, go for a drive then stop and try and fill it again till it overflows.
If you have to put more in, the overflow may be letting water out (or there may be a leak somewhere else.)
If you can’t get anymore in, the gauge is at fault.

We always full until the gauge says 100% and there's water coming out of the overflow. Once we opened the tank at the top to check and when the gauge said 100% and it was overflowing the tank was indeed full.
Alhough we didn't think it was leaking I suspect it's the only answer and will try plugging the overflow as previous posters have suggested

 

[Minxy]

It can't be a faulty gauge as the water comes out of the overflow UNLESS there is air trapped in which is pushing the water out the overflow, but it is unlikely to have both this and a faulty gauge.

Our Globecar 'overflow' is out of the filler which has gaps in the cap, when travelling it seeps out so we always have water streaks down the side of the blooming van! One thing we have to be careful of when filling is that it doesn't get an air block as that make the water come back out and gives the impression its full, when it isn't, this happens with a hose pipe or using containers and a funnel.

As has already been said, it's just gradually coming out of the overflow as you travel - if you fill it and don't move for a couple of days or use the water it should still show full.

 

[Duck Truck]

Careful when bunging up an over flow
Remember it works two ways
Lets the water escape when it's overfilled
Lets air in as you draw water out

If air can't get back in you can damage the fittings
or perhaps the pump won't have enough power to overcome
the vacuum effect.

I think I would leave well alone

 

[Offagain]

Anthea our Bailey water tank is the same as yours. Unfortunately water leaks out of the overflow when you are travelling. Alan has fashioned a "plung" for ours - a cross between a plug & a bung that he pugs into the overflow when we are travelling. When we first discovered it Alan just used some shapeable ear plugs to block it until he could make his "plung".

We couldn't find the outlet for the overflow anywhere accessible in or around the tank so after refilling the tank we've used an ear plug and some duct tape to block it from the outside. We'll see what happens!

 

[Offagain]

Do you drain down between trips, if the heater empties as well it can take half a tank to refill. We have been caught out by that before

We're on one long trip having bought the van in November

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[Lenny HB]

Perhaps that is one of the reasons that my tank does not have an overflow?

Very unlikely, there will be one somewhere.

 

[bigtwin]

We couldn't find the outlet for the overflow anywhere accessible in or around the tank so after refilling the tank we've used an ear plug and some duct tape to block it from the outside. We'll see what happens!

You need to heed this advice:

Careful when bunging up an over flow
Remember it works two ways
Lets the water escape when it's overfilled
Lets air in as you draw water out

If air can't get back in you can damage the fittings
or perhaps the pump won't have enough power to overcome
the vacuum effect.

I think I would leave well alone

For the reasons explained above you may end up in a situation where you have plenty water onboard but are unable to get any out of the taps.

Ian

 

[two]

Be aware that the gauges are usually measuring the depth of water in your tank and it is quite common for the shape of the tank, vertically, not to be linear. You could calibrate your gauge by adding 10 litres at a time from empty (use a clean watering can) and compare the actual litres put in with the capacity displayed by the gauge. I found that half full on my gauge was actually more like 80% in the tank and the gauge showed only three quarters full when the tank was about 95% full.

If yours behaves similarly, you might not be losing as much as you think as you travel but you could try taking the corners less quickly!

 

[tonyidle]

It has been know for the overflow tube to be too low in the tank (lazy/distracted installer) and once full and overflowing will act as a syphon draining the tank until the end of the overlong tube is above the tanks depleted water level.
If the tube is 1/4 way down the inside of the tank then 25% of the water will be syphoned off before the level is below the tube and the syphon suction is broken.
If there's an inspection bung on top of the tank get an arm in and see if you can feel the overflow tube inside the tank.

I can confirm that can be an issue - it's well worth checking before worrying about more complex problems.

 

[tonyidle]

Be aware that the gauges are usually measuring the depth of water in your tank and it is quite common for the shape of the tank, vertically, not to be linear. You could calibrate your gauge by adding 10 litres at a time from empty (use a clean watering can) and compare the actual litres put in with the capacity displayed by the gauge. I found that half full on my gauge was actually more like 80% in the tank and the gauge showed only three quarters full when the tank was about 95% full.

If yours behaves similarly, you might not be losing as much as you think as you travel but you could try taking the corners less quickly!

If it's the most common type of level sensor it comprises 5 rods: one is common & reaches to the bottom; the others are cut to lengths corresponding to the markings on the gauge (approximately ). So as soon as the gauge reads 3/4 the tank level is anywhere between "not quite full" and 3/4 full. When the gauge reads 1/2 full the level can be anywhere between just under 3/4 full and only just 1/2 full. For instance on a 200L tank "1/2 full" means there is between 100L and 150L remaining even if the rods are the correct length and therefore the gauge is accurate. "Empty" would mean you have between 0L and 50L remaining.

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