What's "the fix" for bad fresh water vents?

[dedmiston]

I've seen references to "the fix" for the poorly designed vent tubes for fresh water tanks, but I haven't been able to find it when I search for it.

I just got my fifth wheel back from the dealer for warranty service and one of the items that they supposedly fixed was the faulty vents on my tanks, but I still have the same problem. If I fill my water tanks all the way full, the water will eventually spill out the vents, but the vents extend below the bottom of the tanks (because the tanks are enclosed in the belly). This creates a siphon that drains the water back out of the tanks.

Yesterday I added 90 gallons to my tanks and the siphon began. It kept siphoning for over an hour (I had to leave, so I'm not sure when it actually stopped). When I got back home, I was able to fill another 65 gallons into the tanks. I stopped filling when I heard the gurgling from the vents.

I would really like to completely fill my tanks. We're about to leave for a week of boondocking and it would be nice to start out full.

Does anyone know what the mod is to correct the routing of the vent lines?

Thank you.

 

[johnboytoo]

many put shutoff valves on the outlets for when they have full tanks just for this reason.

 

[dedmiston]

many put shutoff valves on the outlets for when they have full tanks just for this reason.

Interesting idea. Don't the tanks need to vent though? Air needs to fill the void when you run the water pump, right?

 

[Lloyd S]

Maybe they don't have the lines hooked up/ placed correctly.
It seems odd that it would be doing that. You do have a small screen positioned next to the fill opening, don't you? The way I remember, that should have a hose on it that goes back down and hooks onto the top of the water tank.
I wouldn't think there should be any siphoning. Mine doesn't.
When it's siphoning, where exactly is the water coming put of?

 

[Lloyd S]

Here is a pic of my water tank sitting on end on the floor.
The opening on top are pickup for the pump and the other is drain.
The two on the side are fill and vent.

 

[dedmiston]

Maybe they don't have the lines hooked up/ placed correctly.
It seems odd that it would be doing that. You do have a small screen positioned next to the fill opening, don't you? The way I remember, that should have a hose on it that goes back down and hooks onto the top of the water tank.
I wouldn't think there should be any siphoning. Mine doesn't.
When it's siphoning, where exactly is the water coming put of?

No. I wish that's how mine worked.

My fresh water fill is in the "convenience center". It's the top left connection in this photo.

It's hard to see the vents in this photo, but you can see the two streams of water draining out.

The tanks are way in the back over the axles and the fill is up front next to the bathroom.

 

[Lloyd S]

Top picture----------it looks like there is a screen next to that cap. That's a vent.

 

[dedmiston]

Here is a pic of my water tank sitting on end on the floor.
The opening on top are pickup for the pump and the other is drain.
The two on the side are fill and vent.

Do you have an enclosed belly?

(Sounds like a personal question. Apologies for being indelicate.)

 

[Lloyd S]

You might have to bite the bullet and drop the membrane and see if they have a couple lines in there that ain't hooked up properly.

 

[Lloyd S]

Do you have an enclosed belly?

(Sounds like a personal question. Apologies for being indelicate.)

At this distance from you, I don't mind or take any offense.

Yes, there is a membrane on the bottom of my trailer. She's old but has that modern thing.

 

[dedmiston]

Top picture----------it looks like there is a screen next to that cap. That's a vent.

That might just be a remnant from the hardware, like a vestigial tailbone. I don't think it's hooked up. I've never felt any air coming out of it or heard any gurgling that you would expect from a vent.

 

[campmackay]

Check out post #9 from this thread. It gives a good explanation for your issue.

http://www.crossroadsowners.com/forums/f30/fresh-water-drains-10283.html

 

[Travelin' Texans]

One of those lines is a vent which on most rvs is connected to that small screened opening next to the fill port, but CR decided since it would spill into the convenience center to run it below, if you figure which is the vent you could hook it to that spot.
The other line is the over flow & if you've filled the tank completely full then it's doing what it should, relieving pressure off the tank.
Sorry I can't help you you with which line is which on your particular rv.

 

[Lloyd S]

Check out post #9 from this thread. It gives a good explanation for your issue.

http://www.crossroadsowners.com/forums/f30/fresh-water-drains-10283.html

Good find Scott.
I had totally forgot that one. Thanks for digging it out.