Moisture build up underneath fifthwheel

Not normal. Sorry, you have an issue that needs to be addressed. Chances are you can remove the spare tire holder from the frame with 8 bolts. Drop one side of the coroplast and leave the gas line side up there. You will be able to see what the issue is. I did ours last year and replaced the ruined pink insulation with styrofoam insulation. FYI ours was a sink drain pipe was not connected properly.

That was kind of my thoughts also. I was hoping it could possibly be condensation build up between layers. I did notice that there is a small hole in the corplast where the drip is, thinking that's why the hole was there. Thank you very much for your advice.

Towing in a heavy rain can allow water intrusion inside the coroplast. In any case, you need to find water leaking source, and replace any wet insulation. Many, like mine, just have the foil covered bubble wrap insulation, so no need to replace, after getting dried out.

Jerry

Denali2015 wrote:
I was hoping it could possibly be condensation build up between layers.

Highly unlikely......unless the humidity outside is REALLY HIGH and you keep the interior REALLY cold.

Never seen condensation from there. Suspect a leak.

Thanks you for your comment. If it is dry on top of the silver bubble wrap,when I take it off then maybe it's safe to assume it's from rain intrusion...

Denali2015 wrote:
Thanks you for your comment. If it is dry on top of the silver bubble wrap,when I take it off then maybe it's safe to assume it's from rain intrusion...

The silver bubble foil is probably not continuous so a water leak at one spot could run on top of the foil then drop thru at a joint and end up at the lowest point of the coroplast. So just because the top is dry in one spot that does not rule out a water leak elsewhere.

Denali2015 wrote:
Thanks you for your comment. If it is dry on top of the silver bubble wrap,when I take it off then maybe it's safe to assume it's from rain intrusion...

You know if you have recently towed in the rain, or very wet roads. If after that, is when you noticed dripping, I would think it would be the likely reason. Anytime I have towed any distance, with very wet roads, I get some dripping. I think this to be quite common. If you don't get it dried out, it can drip for a long time.

Jerry

We did drive though rain going over Mt. Hood to sisters...that's when I noticed the dripping. Did not give it much attention at that point, thought maybe that was the cause. Came home a week later and parked the trailer. Put a new black tank valve on and did some other maintainence, took it back to storage and then noticed the dripping again. I did have about 4 gallons of water in the gray tank to kind of flush it out. At that point I thought I had a problem but then started thinking it could be condensation between the two layers or residual rain water. Probably better tear it apart just to be sure. I really appreciate all the comments I've received. I'm new to being on a rv forum. Seems like
A good resource with a lot of nice people...

Just a side note to my comment. I'm thinking by moving the trailer the water started dripping again...just a thought I had...