Fresh water won't fill more than 2/3

[dougb-WO]

Filling my fresh water on my 27N causes the water to backflow out of the exterior fill when the tank is only 2/3 full. Seems that the air does not escape from the tank. I need the tank to fill. Ideas?

 

[IOS 3]

Are you relying on the gauge to tell you it's 2/3 full, or visually inspecting the tank from the exterior? On the 27N you can see the water level in the tank from the outside.

 

[dougb-WO]

Are you relying on the gauge to tell you it's 2/3 full, or visually inspecting the tank from the exterior? On the 27N you can see the water level in the tank from the outside.

Relying on the exterior tank view.

 

[Morich]

when we get into wondering about the hidden parts of the RV, I find the interactive parts drawings are often a big help. It lets us look through the walls to see a lot of details we would never know in any other way.
https://catalog3d.winnebagoind.com/menu/Parts.htm
Choose the RV and then go to plumbing for this case?

But I see nothing much to help as it looks like a pretty straight clean shot from the vent to the tank.
Click this snip to get the best picture!


It's the old story of not being able to put anything like water into a closed contailer if there is not a way for air to get out. Water goes in the big pipe and air has to come out the small tube!
So if that doesn't work, about the main point to check is that the small tube is clear from the small vent in the port, down to the tank.

One way to do that might be as simple as holding a tube over the vent and blowing to test air will go in or out? If not, I might be bold enough to move to compressed air with one of the airline ends that have a rubbber type seal to press on the vent and shoot a bit of air in.
Maybe something like spiders built a nest in the line?? Maybe a bit of plastic scrap blocking things right at the vent fitting?
I might recommend starting with low air pressure to avoid simply blowing the tube off a fitting, etc. that creates more problem than fixed!

But worst case might be that it was a poor install and has a built in kink in it that has to be removed! ARGH!!!

See if that seems to help and let us know what you find? Alwasy good to know what others learn as it helps when we get to the same spot!
Best of luck on the chase!

 

[dougb-WO]

when we get into wondering about the hidden parts of the RV, I find the interactive parts drawings are often a big help. It lets us look through the walls to see a lot of details we would never know in any other way.
https://catalog3d.winnebagoind.com/menu/Parts.htm
Choose the RV and then go to plumbing for this case?

But I see nothing much to help as it looks like a pretty straight clean shot from the vent to the tank.
Click this snip to get the best picture!
View attachment 189435

It's the old story of not being able to put anything like water into a closed contailer if there is not a way for air to get out. Water goes in the big pipe and air has to come out the small tube!
So if that doesn't work, about the main point to check is that the small tube is clear from the small vent in the port, down to the tank.

One way to do that might be as simple as holding a tube over the vent and blowing to test air will go in or out? If not, I might be bold enough to move to compressed air with one of the airline ends that have a rubbber type seal to press on the vent and shoot a bit of air in.
Maybe something like spiders built a nest in the line?? Maybe a bit of plastic scrap blocking things right at the vent fitting?
I might recommend starting with low air pressure to avoid simply blowing the tube off a fitting, etc. that creates more problem than fixed!

But worst case might be that it was a poor install and has a built in kink in it that has to be removed! ARGH!!!

See if that seems to help and let us know what you find? Alwasy good to know what others learn as it helps when we get to the same spot!
Best of luck on the chase!

Thanks for those ideas... good ones.

 

[IOS 3]

When the problem occurs are you using the city water connection to fill, and then it backs up to the gravity feed?

Are you able to fill it using gravity feed only?

 

[dougb-WO]

When the problem occurs are you using the city water connection to fill, and then it backs up to the gravity feed?

Are you able to fill it using gravity feed only?

Same backup occurs with either fill method.
This starts when tank is a little over half full. I need a full tank of water for no hookups.

 

[IOS 3]

I wish I could be more help. Agree with Richard (Morich)... it would seem to be a blocked vent line.

 

[dougb-WO]

Except that water comes out of the vent line when backflow is happening out of the intake.

 

[Scotty B]

Did you try opening the gravity fill door and using the fill handle in the wet bay to add water?

 

[dougb-WO]

Not both at once. I will try that tomorrow. Thanks much

 

[Scotty B]

Think it says in the manual to open that other fill door when using the internal fill...lets the air escape

 

[dougb-WO]

Thanks. I will try that.

 

[Morich]

Looking further at how the fill/vent, etc. fit, it looks hard to get the water to come back up the vent line or the gravity fill if the tank is not totally past full
OR
if the RV is on a pretty serious slope so the passenger side is high enough to let air be trapped on the far side and not able to go up and out the vent?
But then if you are looking at the tank water level on the wet bay side, it seems like you would not see 2/3 but more like totally full?

If the red line is the floor level and water goes in and gets high enough to run UP the fill or vent line? I'm not seeing how that can happen?


Maybe the gravity fill and vent line are run too far and too much horizontal for them to actually drain into the tank well?

So, is there any thought that there was water in the vent line and as the air came up, it was forcing some water along ahead of it to come out where you could see it?

Maybe try blowing the lines out to clear them and see if it happens again?

Weird seems normal at times, so just throwing in ideas for you to consider!!

 

[dougb-WO]

I appreciate your ideas . To further explain....
The moho is level
The water that backflows does so with a lot of pressure. It shoots out with high pressure. This is what is confusing. Why does water from the fresh tank start blasting out of the outside fill when the level in the tank is a little over half full? This prevents filling the tank completely. The water going in through my hose is coming out as fast as it is going in.

 

[IOS 3]

Very confusing. So, visual inspection of the freshwater tank shows 2/3 full. Does the gauge panel inside the rig also show only 2/3 full?

 

[Morich]

Well, that is a major biggie!
Looking further, it really shows no reason or way that should happen.
But it does and that is the big one for today!


Normal would seem to be the water comes in at top center of tank, falls to floor of tank and no way get out the vent or gravity fill undtil the tank is overflowing!
Water goes in , air goes out to let it happen!

One truly weird and impossible to check idea?
If the vent and gravity fill lines are extended way past the normal at the top of the tank adn go down to about the 2/3 level?
As water goes in under pressure, air goes out the vent, until the water covers the end of the gravity fill and air vent line.
When both these are covered in water and more water is shooting in, the air can't go out but water will!



Goofy idea and insane that the two vent and gravity fill lines would extend that far into the tank?
Nearly impossible to tell what is inside the tank and condition of the lines without dropping the tank ??

 

[Morich]

Okay, to further add to the idea I'm insane?
It seems this should have been a warrenty item long past! Likely way too late now for that, so what else might fix the problem?

If this is really what is wrong, maybe DIY is needed.
The problem would be that the air can't go down to get out the vent, so what if one added a vent? A vent drilled trhough the plastic near top as it should have been, would let air go out until the water reached that new vent level. Water would not have to move out to let new in!
Maybe consider drilling a 1/8 inch hole near the tank top to test if it is the solution? Something that might be used for a valve or sealed if it doesn't work? For this use a screw forced into the plastic might be good enough to seal the mistake??

Since it should not be under pressure, maybe a simple vent fitting pressed, glued, etc. into the top with a line of simple aquarium airline would be enough?
If there is concern with water sloshing out this line, maybe add a simple valve at some point where it is handy to open when filling, close when done?
If the side of tank is handy to view, maybe just a plastic airline valve like used for fish tanks and no tubing needed. Open to add water, close to keep it from splashing out?

I fully admit, this is way beyond what we SHOULD have to do! But isn't that what we have to deal with?

 

[dougb-WO]

Much thanks again. That is the same diagnosis that i have come up with. I'm hoping to try a new remedy today.

 

[dkoldman]

This is crazy. With all of the info I have read thus far it makes me think of one thing that I have seen do similar. Maybe it creates an idea for someone.

I have Saltwater tank, when I drain I using a siphon pump. I am trying to visualize if I have siphon in fixed position where 1/2 tank provides enough pressure head restart the siphoning. The pressure coming out my Siphon tube is function of weight of water. Have you eyeballed exactly with overflow come out of tank?

In my tank, I can see the water tanks water level and overflow at the same time. It would be impossible for water to come out that overflow unless the tank water lever was raise to level of the input.