Water between Reflectix and Coroplast layers

**fmartinmn** · 07-19-2021, 05:39 AM

We have a new to us 3350 S class. It came with a slight stale water odor, not always, comes and goes. Sometimes stronger than others.

I checked all the waste and supply line connections inside the unit, no leaks
I removed the shower access panel and checked for leaks
I checked the air admittance valves, not stuck
I pulled the panels in the basement and checked the gate valves, waste and supply line connections, again, no leaks, all dry in there, no leaks behind nautilus panel
I checked the a/c drain pans on the roof, working fine
I dropped the coroplast and found a thin layer of water between the layer of reflectix and the layer of coroplast. The top of the reflectix is completely dry
I am stymied about the source of the water?
Could it be condensation?

All additional ideas are greatly appreciated. Thanks, Frank.

**NB Canada** · 07-19-2021, 06:07 AM

Could it be road water

2021 Imagine 2400 BH
2018 GMC Sierra 4x4 crew

**fmartinmn** · 07-19-2021, 07:34 AM

Originally Posted by NB Canada

Could it be road water

2021 Imagine 2400 BH
2018 GMC Sierra 4x4 crew

It is possible but the exterior integrity of the coroplast looks good, the previous owner had it parked on a permanent site and I first noticed the slight odor even there. So, if it is external water incursion, it would have to be rain water. Trailer has been in storage for almost 3 weeks. It has been unusually dry here in MN.

**JonSr.** · 07-21-2021, 12:21 PM

Originally Posted by fmartinmn

We have a new to us 3350 S class. It came with a slight stale water odor, not always, comes and goes. Sometimes stronger than others.

I checked all the waste and supply line connections inside the unit, no leaks
I removed the shower access panel and checked for leaks
I checked the air admittance valves, not stuck
I pulled the panels in the basement and checked the gate valves, waste and supply line connections, again, no leaks, all dry in there, no leaks behind nautilus panel
I checked the a/c drain pans on the roof, working fine
I dropped the coroplast and found a thin layer of water between the layer of reflectix and the layer of coroplast. The top of the reflectix is completely dry
I am stymied about the source of the water?
Could it be condensation?

All additional ideas are greatly appreciated. Thanks, Frank.

Surprisingly, I noticed the same problem on our 2019 372WB last week. I had to drop the coroplast for different reason and found water between the coroplast and the reflectix. What makes it even more hard to understand the situation is the water was only in the rear of the rv, the last 3-4 feet from the rear. No water elsewhere. I first thought it was condensation, and it still may be that. It definitely wasn't road/rain water from driving in the rain, as I had previously installed aluminum bar stock in place of the straping used by GD to hold up the coroplast when we first got the RV - a lesson I learned from another rv to seal the coroplast tightly to the frame. As there is no plumbing or other openings in the rear of a 372, I'm stuck with the condensation theory. Maybe someone else has more thoughts on this.

**thegreenblade** · 07-21-2021, 08:30 PM

Dang,same problem I had by the grey tank pull handle. Water was leaking through the slit where the wire comes out to the handle. I took the Coroplast off and I didn’t see any water on top. Further investigation I figured it was road water that got in between the honeycomb of the coroplast. It was a lot of water seeping out when I was parked. Crazy I couldn’t see any on top.

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**fmartinmn** · 07-22-2021, 05:59 AM

Originally Posted by JonSr.

Surprisingly, I noticed the same problem on our 2019 372WB last week. I had to drop the coroplast for different reason and found water between the coroplast and the reflectix. What makes it even more hard to understand the situation is the water was only in the rear of the rv, the last 3-4 feet from the rear. No water elsewhere. I first thought it was condensation, and it still may be that. It definitely wasn't road/rain water from driving in the rain, as I had previously installed aluminum bar stock in place of the straping used by GD to hold up the coroplast when we first got the RV - a lesson I learned from another rv to seal the coroplast tightly to the frame. As there is no plumbing or other openings in the rear of a 372, I'm stuck with the condensation theory. Maybe someone else has more thoughts on this.

I am going to dig into it more deeply next week when I have more time. @steve147 gave me a heads up about the washing machine valves up front. I haven't checked those yet.

**fmartinmn** · 07-22-2021, 06:07 AM

Originally Posted by thegreenblade

Dang,same problem I had by the grey tank pull handle. Water was leaking through the slit where the wire comes out to the handle. I took the Coroplast off and I didn’t see any water on top. Further investigation I figured it was road water that got in between the honeycomb of the coroplast. It was a lot of water seeping out when I was parked. Crazy I couldn’t see any on top.

Sent from my iPhone using Tapatalk

In my case, the odor was present when I picked it from a seasonal site. It had not been towed in over a year. So, I don't believe I am dealing with road water. At the start of a trip, little to no odor, after 4 days of use, odor becomes very noticeable. I will keep digging.

**Steven@147** · 07-22-2021, 08:36 AM

Originally Posted by fmartinmn

I am going to dig into it more deeply next week when I have more time. @steve147 gave me a heads up about the washing machine valves up front. I haven't checked those yet.

I wish you luck Frank in finding the problem. We don't have a clothes washer installed in the front closet either but I purge the clothes washer water lines anyway from time to time, if not the water trapped in those lines will get stale and stink, I also check the valves for leaks, they are not the best quality valves and can leak.
I also make sure the cap on the clothes washer drain line in the closet is tight.

In any case if you have water down on the coroplast in sufficient quantities, and not driven in a lot of rain, then you mostly likely have a leak, either in the fresh water line system or the plumbing drain system. Regards to the fresh water system - From time to time I'll switch over to the demand pump on the fresh water tank system, once the pump builds pressure and shuts off, if it stays off for over 30 minutes then I assume there are no leaks in the fresh water system, hot or cold water lines..

Now in the plumbing drain system, I replaced the AAV valves long ago with better quality ones from home depot. We get a foul odor from the bathroom once in awhile. Either from the shower drain or up through the two bathroom sink drains. It usually means our grey tank 1 is getting full or the traps for the shower or bathroom sinks are dry.
And the shower drain flows into the grey tank 1 vent pipe stack instead of directly into the waste tank or "T" into the sink drains, this sometimes allows grey tank 1 foul odors from the vent stack to come up through the shower drain. Also if the grey tank 1 has gotten too full, shower drain water backs up in its drain line then partially blocks the grey tank 1 vent line stack. I wished they would never have plumbed the shower drain into the grey tank 1 vent stack. But we have never had water lying down on the coroplast.

I attached the crude plumbing schematic I made for our 3350RL. This took a lot of time tracking down all the drain lines and figuring out how they had everything connected. Maybe it an be of help to you.

**fmartinmn** · 07-22-2021, 09:18 AM

Originally Posted by Steven@147

I wish you luck Frank in finding the problem. We don't have a clothes washer installed in the front closet either but I purge the clothes washer water lines anyway from time to time, if not the water trapped in those lines will get stale and stink, I also check the valves for leaks, they are not the best quality valves and can leak.
I also make sure the cap on the clothes washer drain line in the closet is tight.

In any case if you have water down on the coroplast in sufficient quantities, and not driven in a lot of rain, then you mostly likely have a leak, either in the fresh water line system or the plumbing drain system. Regards to the fresh water system - From time to time I'll switch over to the demand pump on the fresh water tank system, once the pump builds pressure and shuts off, if it stays off for over 30 minutes then I assume there are no leaks in the fresh water system, hot or cold water lines..

Now in the plumbing drain system, I replaced the AAV valves long ago with better quality ones from home depot. We get a foul odor from the bathroom once in awhile. Either from the shower drain or up through the two bathroom sink drains. It usually means our grey tank 1 is getting full or the traps for the shower or bathroom sinks are dry.
And the shower drain flows into the grey tank 1 vent pipe stack instead of directly into the waste tank or "T" into the sink drains, this sometimes allows grey tank 1 foul odors from the vent stack to come up through the shower drain. Also if the grey tank 1 has gotten too full, shower drain water backs up in its drain line then partially blocks the grey tank 1 vent line stack. I wished they would never have plumbed the shower drain into the grey tank 1 vent stack. But we have never had water lying down on the coroplast.

I attached the crude plumbing schematic I made for our 3350RL. This took a lot of time tracking down all the drain lines and figuring out how they had everything connected. Maybe it an be of help to you.

Thanks again Steve, I saved the drawing and will use it next week when I get back to the trailer. I will post my findings.