2011 Big Country 3450TS water collecting above water\moisture barrier closer to the back of RV

We've noticed that water is collecting above the water\moisture barrier at about the back half of the RV. We live in the unit full time. Looked and looked for where this water might be getting in, but have been unable to locate any leaks or such. Has anyone else encountered this problem? Any thoughts or ideas?
 
Could you explain a little further what water/moisture barrier you're referring to.

Its the black colored barrier that runs underneath the entire length\width of the RV, with the exception of the slides. If you were to remove it, you would then see the underside of the floors in the RV. There's one at the front as well as one at the back of the RV, and its the one at the back that is collecting the water ... I think I've also heard it referred to as a vapor barrier.
 

danemayer

Well-known member
Sounds like you're talking about the corrugated plastic (coroplast) underbelly enclosure. Water accumulating in the rear section is most likely from either the fresh water tank, or from water spun up by the tires while driving through rain. But if it's stinky, it's probably from the kitchen gray holding tank.

If it's road water, an easy way to deal with it is to carefully drill a few 1/4" holes in the lowest areas of the coroplast. Put tape on the drill bit with 1/4" of bit sticking out from the tape. That'll help you keep from drilling further than necessary and maybe contacting something above the coroplast.

If you want to probe a bit further, you can remove several of the coroplast mounting screws from the off-door-side. You should be able to pull the plastic down a few inches to shine a flashlight in and see if anything looks amiss. The mounting screws will come out much more easily with an impact wrench. You can remove them with a socket wrench, but it's much harder and more likely you could shear off the head of the screw.

You can also gain access by cutting the coroplast. If you make a rectangular cut, leaving the front edge intact, you can bend it down to get a good look inside. The fresh tank fill and drain connections are above where the drain hose comes through. If you have a leak, that's probably where it is leaking. When done, you can tape the coroplast closed.
 

TravelTiger

Founding Texas-West Chapter Leaders-Retired
Its the black colored barrier that runs underneath the entire length\width of the RV, with the exception of the slides. If you were to remove it, you would then see the underside of the floors in the RV. There's one at the front as well as one at the back of the RV, and its the one at the back that is collecting the water ... I think I've also heard it referred to as a vapor barrier.

That underbelly material is called Coroplast, and is not water-tight.

The water can be a leak or just water from your tires if you've driven in rain. There should be a layer of metallic-looking bubble-wrap insulation, as well. If you remove some of the screws from the coroplast you should be able to see/feel -- is there water above the insulation (suggesting leak) or below it (suggesting road water).


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Yes, the water is collecting above the coroplast underbelly enclosure you had mentioned (Now I know what its called).
The water seems to collect at the back 1/3 or so area of the RV.
We put a few small holes in the coroplast, this drains some water continuously, and then every couple of months, remove a few screws, bend the coroplast downwards, and that drains most of the rest of it, but then over time it re-collects.
We live in the unit full time, and the RV never moves, so no water from tires.
We do not use the freshwater tank at all, and its empty, and the water pump is off.
Could it still be the freshwater tank? or a connection to the freshwater tank?
And if so, would you know where the freshwater tank is, in relation to the kitchen sink?
The water that does collect is very clear, and does not have any sort of odor.
We live on Vancouver Island, and it rains here all of the time, as in pretty much every day, from late October into early April, and we have always thought that it was likely the rain getting in somewhere near the back of the RV. We first noticed the water accumulation last November, and am unsure if it was there prior to that,
We've looked and looked for entry points for the rainwater, but have been unable to locate any.
Also we've noticed that the water collects above the coroplast, but is below the tin-foil like layer that runs along the top of the coroplast (I'm not sure what the tin-foil thing is called)? I think that its used to trap heat?
 

danemayer

Well-known member
The tin foil is a radiant heat barrier - a type of insulation.

Let me suggest you open the fresh tank drain valve. The fresh tank is usually located over the axles for weight distribution, and there is a PEX tube sticking out of the coroplast, closer to the off-door-side, and probably just in front of the front axle. If water comes out of the fresh tank, it may be filling by itself. On a 2011 model, that would mean the internal check valve in the water pump is stuck partially open.

But if the water is accumulating between the radiant heat foil and the coroplast, that suggests a different problem. The coroplast is tucked into the rear cap. If water were running inside the cap, it could flow on top of the coroplast and under the radiant foil. Have you closely inspected the caulking on the roof, along the seams, in corners, at the ladder mounts, and around lights? Try pulling it to see if anything moves.
 
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