Water tank massive air lock

Submitted: Sunday, May 20, 2018 at 22:02
ThreadID: 136738 Views:8808 Replies:10 FollowUps:8
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Per my earlier posting after a few ideas, however suspect I am on the right track.

Twice I have had the issue with folks camper that I go and "fill the tanks" have water flowing back at me after a short time (within 1 or 2 nminutes) pack up hoses etc drive off to middle of "nowhere eneter captive audince place here"

And then discover after 2 maybe 3 kettles worth of water pump stops working and tap test on tanks indicate there is no water in either tank !

No water level guages fitted either tanks have hollows in them to act as baffles for surging

Tanks have a air vent hose attached to filler neck similar to those fitted to a say a vehicle fuel tank where fuel spurts out of a small tube down filler neck so pump knows when to automatically switch off.

The vent hole is minsiule by comparison to that of filler hose, I ended up drilling one of them out to 8mm but old man wasn't too impressed about "dust ingression" so two additional fuel filters were put in place to prevent this dust ingression from occurring and then to ässist with "air removal" a length of pipe was placed between air lines by the old man - honestly think its made it worse not better

To prevent excessive filling rate I add on a length of hose with a 2nd irrigation tap allowing me to control flow rate to some extent, also means I can fill the internal tank in prado without having a 2nd person to turn main tap off

So how does one get rid of the air lock ?

Is it a common problem with other vans or does it sound like something isn't right with the system itself or possible tank manufacture ? by comparison at a similar flow rate take me a good 5 mins to fill the 40 + l tank in Prado (boab dolium front runner style)

I discussed the issue with some knowledgeable folks at a geraldton marine chandelry shop who suggested using a fuel tank breather stainless steel tail barb end with a small guaze filter head attached -so curious to know if anybdoy has fitted them before ?

considering the cost of one I hope this will work properly !

open to commonsense suggestions and paractical experince with same issue
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Reply By: Gronk - Sunday, May 20, 2018 at 22:41

Sunday, May 20, 2018 at 22:41
I have 2 tanks on a small van and have never filled them via the fill point up high.

I have a brass tap and fitting screwed into the drain points at the bottom of the tanks and fill with a garden hose "clicked" onto it.

Fill fairly slowly, and when the air has stopped escaping and water is flowing freely out the fill point, the tanks are full.
AnswerID: 619042

Follow Up By: Darian - Monday, May 21, 2018 at 21:40

Monday, May 21, 2018 at 21:40
Me too...my van has 3 x 80 litre water tanks...the 3 fill points are at the rear with the two rear tanks. No way will the somewhat remote front tank breathe properly when trying to get water in at that fill point. The solution was to extend the front tank's drain point out to the A frame, using quality hose and a snap on fitting. Back filling is the go. A pity we have to chase these things up.....that's the Aussie van industry.
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Reply By: Ozhumvee - Monday, May 21, 2018 at 06:34

Monday, May 21, 2018 at 06:34
The problem is that if the air can't get out at the same rate the water is going in then you will have problems, the tank breather must be large enough for the air to escape. My tanks don't have a filler as such but have a hose click on fitting which allows filling with a hose, the breather is the same size pipe as the filler.
AnswerID: 619043

Reply By: Sand Man (SA) - Monday, May 21, 2018 at 07:58

Monday, May 21, 2018 at 07:58
I had a similar problem with my camper and solved it by rerouting the breather up the rear bumper support bracket and out the back. I terminated the breather with a small fuel filter fitting.
The original breather hose ran from the tank across to the side, then undulated along the chassis frame to the front right hand side, where the filler was located.
No way was this route going to work with water continually blocking the breather hose.

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AnswerID: 619045

Reply By: Banjo (WA) - Monday, May 21, 2018 at 08:13

Monday, May 21, 2018 at 08:13
My breather hose has a dip in it before it turns up to fit onto the connection near the filler opening. There is no way to route the hose to avoid that due to chassis cross members.

This dip fills with water and impedes the air trying to escape.

So I added a click-on hose connection at the dip point. When filling I separate the connection to release any water, so that air has a free flow out up to the filler connection.

Then I either re-connect and wait for the air to escape out through the vent near the inlet, or alternatively leave it unconnected and when water starts coming out from there I know the tank is full.
AnswerID: 619047

Reply By: Malcom M - Monday, May 21, 2018 at 08:32

Monday, May 21, 2018 at 08:32
You have a plumbing issue.The venting air should push out any water plug in teh vent hose.

The vent to filler size ratio can happily be 5 to 1 ie 25mm filler and 5mm vent.
The venting air will compress so will escape ok provided the hose isn't kinked or have mud blockages etc. This compressed air clears out any water plug in the vent hose.
Having a bigger vent hose makes it a whole lot harder for the escaping air to push that plug of water out of the vent hose.

Widening the vent may also allow more crap to enter the vent hose and solidify but that depends on the filler caps design which may well block both hoses completely when the cap is fitted. Camec for instance.

Restricting your fill rate again says you have a fundamental plumbing problem.
Rather than curing the symptoms, I'd be putting time into figuring out whats wrong with the basic plumbing first.
AnswerID: 619048

Follow Up By: Sand Man (SA) - Monday, May 21, 2018 at 16:07

Monday, May 21, 2018 at 16:07
I disagree Malcolm.

The problem in my case was several low lying areas as the breather hose dipped under the chassis rail then up again. about 6-8 dips in all. No way was this going to blow water out once it got in. It was like it since brand new.
Just simple engineering design fault with my van.

I simply disconnected the breather hose from the top of the water tank and added a new breather hose, rerouted it up the left hand bumper support bracket.
Fixed the problem at minimal cost and effort.

I had a similar problem with the sink drainage. The corrugated hose ran down to the chassis, then undulated across to the other side of the van. The water wouldn't drain from the sink properly. This time I pulled the hose back to the sink side of the van (in my case the left side), routed it downwards with an elbow and added a coupling to attach the hose to.

These were the only two design faults I found on my otherwise excellent Camper Van.

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Follow Up By: HKB Electronics - Monday, May 21, 2018 at 21:20

Monday, May 21, 2018 at 21:20
Can only speak from my experience with my setup, the breather hose drops below the tank on its way back to the filler. The breather hose is hard black tubing probably about 8mm internal diameter. When I start to fill the tanks any water in the breather tubes is squirted out the breather hole in the filler assembly.

The breather tubes fill with water when I fill the tanks as I fill then to the top of the fillers and can see the last of the air bubbles leaving the filler tube. The fill rate slows once water starts backing up the breather tube.

In my case breather lines would only be about a metre and half long, the pressure in the tank has no problems clearing the breather lines, however if I do try to fill the tanks from mains pressure with the taps open wide it will blow water back out fillers as the fill tubes and gravity affect just can't handle the flow, so I simply back off the flow rate till they can.

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Reply By: RMD - Monday, May 21, 2018 at 08:38

Monday, May 21, 2018 at 08:38
If filling an empty tank, or near empty, you will know for sure the time taken to overflow is far less time than it takes to actually get water into the tank, therefore just that alone will indicate the tank is not full. No good driving to the camp to find the tank is empty when it cannot possibly be full because of the amount of water you didn't add to the tank.

A small fuel filter will not pass air fast enough to cater for a filling rate with a hose and so that will stall the process too. Try blowing air with your mouth through a small fuel filter to see. Free flow exit air is best as others have mentioned.
Depending on where the breather hose exits the tank it would be a sensible idea to have that point the highest when filling.

PS, the breather in a petrol/diesel filler, positoned in a similar position to your in the water tank system, has nothing at all to do with telling the pump hose when to cut off. It can spurt or pass air but doesn't control the cutoff.
That is done by, when a pressure difference happens in the small hole at the end of the nozzle and that turns the nozzle off. Absolutely nothing to do with what the tank airbleed is doing or where it is positioned..
AnswerID: 619049

Reply By: Dean K3 - Monday, May 21, 2018 at 18:15

Monday, May 21, 2018 at 18:15
Took this picture of the piping which sits internally inside camper unit.

black pipes are the water inlets and ones with filter attached the air vent pipes.

A few folks have mentioned dips or low points in the pipe route, I concur this would be a issue if it had a signifcant rise n fall, appears that both pipe are basically level until they come through floor to meet up with filler section.

Convinced the fuel filters won't help period and adding the cross over pipe won't be assiting either.
AnswerID: 619057

Follow Up By: RMD - Monday, May 21, 2018 at 22:20

Monday, May 21, 2018 at 22:20
The fuel filters don't look to be big in size of barb and if you blow air through them with your mouth it isn't real easy. Only the pressure of water displacing air is what causes the air to escape. Nil restriction to airflow means water is allowed to enter.
The filters are the wrong way around for dust filtering, ok for fluid direction but you aren't trying to filter the water with the filters. Also, as soon as the filters get any water on them they will become restrictive to water and airflow. they are made to pass petrol not water. Try breathing through a wet face washer and see what effect the water has over a dry face washer.The idea is good, it is just they are not suited to the task.
Just a stainless mesh or piece of expanded aluminium sheet rolled up, is a decent filter which doesn't hold back air but stops bugs etc.
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Reply By: Member - Blue M - Monday, May 21, 2018 at 21:58

Monday, May 21, 2018 at 21:58
Filling the front tank on my van used to cause me grief with what I thought was an airlock. After about a week I found out some little mongrel hornets decided to build a mud nest down inside the air vent pipe where the hose is secured to the actual filler.
After I found out what the problem was, I now put a little bit of fine twisted wire in the air vent pipe, enough to let the air pass, but enough to keep the hornets out.
I also thought it was the way the pipes dipped around the chassis as well, but they were not the cause my problems.
AnswerID: 619065

Reply By: Nomadic Navara - Tuesday, May 22, 2018 at 08:05

Tuesday, May 22, 2018 at 08:05
How are you filling your tank? I have found that I needed to force the water out of the breather tubes in some installations before the tanks would fill. I have a 400 mm length of hose that I join to the supply hose with the fitting pictured below. I poke at least 200 mm of that hose down the filler pipe in the van. The venturi effect of the water flowing down into the tank produces sufficient pressure in the system to clear the water from the breather hoses. There is no seal between the fi1/2" hose in the 1" hose will not produce enough pressure to damage your campers water system.
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Follow Up By: Dean K3 - Tuesday, May 22, 2018 at 17:06

Tuesday, May 22, 2018 at 17:06
G'day Peter, its a intesrting comment you make !

I manaaged to find the tank manufacturer called Enmach based over in Bundy berg Qld

I downloaded the specs sheet from thier website, and one of the clearly stated limitations is:

This tank is not to be pressure filled from a hose that is connected from a mains pressure to tank that has a larger flow rate than the breather. Doing so will cause the tank to inflate and split voding warranty

Call me slightly confuzzled here but that mean you can't fill these tanks from any form of main water supply - and if the delivery pipe is larger than air escape line this will also cause problems. - which is obviosuly is do so.

I removed the airline at a convenient joiner in pipe work, soon as I started filling water from tap I had water flowing good n steady out of the airvent line - tomorrow shall increase length of line to above water tank and see if this helps or not

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Follow Up By: Member - Rowdy6032 (WA) - Tuesday, May 22, 2018 at 18:41

Tuesday, May 22, 2018 at 18:41
The instructions that come from the manufacturer of my van stated that when you fill the tanks you should only use half or less mains hose pressure to fill the tanks.

I have had no problems when doing this but it can take some time. Just a matter of putting the hose in and finding something to occupy yourself for a while. Is fine at home but could be a problem if trying to top up along the road.

When you increase the mains hose pressure I have the same difficulties you face with blowback.

Suggest you turn the pressure down.

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Follow Up By: Dean K3 - Tuesday, May 22, 2018 at 19:12

Tuesday, May 22, 2018 at 19:12
easier said than done when you have queue behind you and some asking how long will you be !

even though I just got there - some have no patience trust me

Will have a convo with the local manufacturer of rotamoulded tanks nearby, I have one of thier 80l variants sitting as a dust colector (dumped by former work place and thought hmm good to have one day) as a test I filled that up no problems at mains flow (full rate) and took 10 odd minutes
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Follow Up By: Nomadic Navara - Tuesday, May 22, 2018 at 22:18

Tuesday, May 22, 2018 at 22:18
Quote - "This tank is not to be pressure filled from a hose that is connected from a mains pressure to tank that has a larger flow rate than the breather. Doing so will cause the tank to inflate and split voding warranty"

I agree with that but it is a matter of how much you pressuriser the tank. What they generally mean is do not connect the mains hose directly to the tank. What I said above was to poke the mains hose down the filler. The gap between the outside diameter of the mains hose and the internal diameter of the filler hose will provide sufficient escape of air so the tank will not explode but it will expel the little bit of water in the breather hose. I have been doing that for 15 years without any problem.
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Reply By: Dean K3 - Wednesday, May 23, 2018 at 19:11

Wednesday, May 23, 2018 at 19:11
Bit of an update for those who maybe interested - please accept its just a early result I have.

I spoke to rotamoulding who make various water diesel tanks for multiple applications who advised that the 1/2 3/8 airline would be sufficent for the air to escape he mentioned he reverse fills his water tank on a ute with no issues -nor did I have any issues with filling the 80l unit i sourced from them few years ago for another project.

This narrows down the mains pressure being the issue, only thing is most water taps don't have a pressure control valve fitted unless a plumber has done it for manufactuere purposes for water heater or similar.

So thinking outside the box I wandered into one of the better irrigation supply shops nearby, had a convo with them and said " Oh you need one of these things"

the white bit is a 15 PSI (1.03 bar) pressure regulator rated at 1.9 to 57 LPM manufactured by Senniger Irrigation and a few extra sockets - allows me to attach to a water supply tap and then at other end attach food garde hose to fill the tank.

In thoery I now have two completely filled tanks I coudl hear air bubblign around for quite some time and then water coming out the filler inlet few minutes later -unlike within 30 seconds like before.

Still do do some further testing see if I can get more water into tanks but if this solves the issue then I'm happy bloke again - just need to get pump to work again - another gremlin with this system (mounted externally underneath with dust n crap flying around)

AnswerID: 619101

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