Wet bay floor replacement

[oldwildman]

So, we bought our rv this summer. Only one trip so far but we really like it. Had it inspected by a certified inspector. He missed some damage to the wet bay floor. A little annoyed as I found out later that it's a common issue with our model and it was fairly obvious had he looked. Oh well, if that's the worst problem we have, I'll be a happy boy.

I'm planning on replacing the floor this Spring. It's a convenient 4'x8'. Planning on using pressure treated 3/4 plywood with several coats of marine paint. Then, on the inside, using a heavy duty plastic/fiberglass panel with Dacor on the corners. Sound like a good plan?

Now the real question. I saw a video online about replacing the floor. They recommended taking out the freshwater tank (leaving the waste tanks in), cutting the legs for the waste tank supports and folding up and over. Then hammering the flange that hold the door weatherstripping sideways so you can slide the new panel in. Not very impressed with that way of doing it.

What I want to do is remove all the tanks so that I can slide the whole new floor in, in one piece, without damaging anything. I'm very good at plumbing. Plumbed many a bathroom in my time. It's just abs drains and pex water lines. And yes, I realize that the waste tanks are going to be more than a bit messy. My main concern is how the abs transitions into the waste tanks. I can't really see things until I start dismantling things. Is it like a fernco fitting? Or something similar that's easy to work with? Or, is it problematic as it's a 20 year old MH?

 

[Gary RV_Wizard]

The method of replacement and alternatives for doing it would be totally dependent on the particular RV design and construction. Some photos wold help get some meaningful replies.

 

[oldwildman]

The method of replacement and alternatives for doing it would be totally dependent on the particular RV design and construction. Some photos wold help get some meaningful replies.

Hard to get a pic of anything except the panel that has the freshwater valving on it. I can obviously see the waste drain lines where I access them to drain. But, the tank hookup is up behind a panel that prevents a good line of sight.

I have most of it figured out. It's basically a full 4' wide, 2' high, bay the width (8') of the coach. Flat bottom the whole way. Just a big rectangular box. The front and back walls are I'm guessing plywood or fiberboard with a fiberglass/plastic face. As is the existing bay floor. The floor perimeter sits on a 1 1/2" steel flange that is part of the frame of the coach. Once I get the clearance, the new floor should just drop into place.

The reason everything has to come out is the non removable (and probably structural) flanges that hold the weatherstripping for the doors. They narrow the width of the opening 1 1/2 - 2" on each side. So, for the new floor to go in in one piece, the 48" plywood has to be tilted quite a bit to make it through a 44-45" wide opening. And the tanks prevent that.

The freshwater tank is a large flat tank that lays on the floor. I can see the hookup for that. Seems to be just a nipple that the pex connects to. I'll just cut the pex and put a coupling on it when reinstalling. There is a rectangular steel stand made of 3/4" square stock with legs that supports the waste tanks above the freshwater tanks. The legs just seem to sit on the bay floor.

The part that has me worried is the abs to tank connections. And I can't put eyes, or camera lense, on it until I start taking things apart. One side has a panel with all the freshwater plumbing valves and such that goes almost the the floor of the bay. The other side has a panel that is screwed on. The bedroom/basement heating unit is there and I'm betting it has to come out before I can see anything in that area.

Is there sort of a 'common' way that the piping is hooked to the waste tanks? Or does every manufacturer do it different? It's hard to cut abs without a lot of vibration. It would help if I knew the nature of that connection so I'm prepared before I start. I'd hate to start and find that I have to order new tanks and leave the unit laying in pieces in the driveway for a week or two.

 

[oldwildman]

Here's the video. The part I don't like is at around 7 minutes in.

https://www.google.com/search?q=tif...ate=ive&vld=cid:65d3c216,vid:zDTzthBEYgY,st:0

 

[Onyrlef]

When you say some damage, how badly is it damaged and where? I watched the entire video, pita and what could go wrong are both understatements. Speaking for myself I'd be looking for any alternative to that operation that may not be perfect, but would be good.

 

[oldwildman]

When you say some damage, how badly is it damaged and where? I watched the entire video, pita and what could go wrong are both understatements. Speaking for myself I'd be looking for any alternative to that operation that may not be perfect, but would be good.

Thanks for taking the time to view the whole video!!! A bit of a sledgehammer mechanic fix, isn't it? Yes, there are many parts of the way that they do it that are problematic. A few brute force solutions. But all the troublesome parts could be eliminated by pulling the waste tanks.

The original floor has a thick plastic sheet on top and a thin coating (plastic?) on the bottom. Hard to tell what the substrate is without causing more problems. But, feeling through the bottom plastic, it almost seems that it's a particle board of some type. Or, badly deteriorated plywood. It's badly damaged. The thick plastic on top is what's holding that area together at this point.

Very hesitant to replace just the bad area. The junction between old and new would tend to allow water penetration into the substrate. And it doesn't seem to be of good quality already. If I'm going to tear into that area, I only want to have to do it once.

The splash screen before the video starts has a good view of the problem area. Looking in, the bad area starts at right edge of the drain basin. It extends on that line, parallel to the side wall approx 2 feet or so into the compartment. Unfortunately, one of the corner legs for the waste tank support sits on the bad section. I can put in a temporary plate to transfer the weight to the flange that supports the floor until I get the time to properly fix things later this coming year.

After doing some more looking online, I think that the connections to the tanks may be threaded fittings. That would certainly make the job easier. Or, should I say, less difficult.

I've read that Tiffin makes a composite replacement floor. But, from what I've read online, getting it delivered is a problem. I'm going to call and see.

 

[Onyrlef]

Thanks for taking the time to view the whole video!!! A bit of a sledgehammer mechanic fix, isn't it? Yes, there are many parts of the way that they do it that are problematic. A few brute force solutions. But all the troublesome parts could be eliminated by pulling the waste tanks.

The original floor has a thick plastic sheet on top and a thin coating (plastic?) on the bottom. Hard to tell what the substrate is without causing more problems. But, feeling through the bottom plastic, it almost seems that it's a particle board of some type. Or, badly deteriorated plywood. It's badly damaged. The thick plastic on top is what's holding that area together at this point.

Very hesitant to replace just the bad area. The junction between old and new would tend to allow water penetration into the substrate. And it doesn't seem to be of good quality already. If I'm going to tear into that area, I only want to have to do it once.

The splash screen before the video starts has a good view of the problem area. Looking in, the bad area starts at right edge of the drain basin. It extends on that line, parallel to the side wall approx 2 feet or so into the compartment. Unfortunately, one of the corner legs for the waste tank support sits on the bad section. I can put in a temporary plate to transfer the weight to the flange that supports the floor until I get the time to properly fix things later this coming year.

After doing some more looking online, I think that the connections to the tanks may be threaded fittings. That would certainly make the job easier. Or, should I say, less difficult.

I've read that Tiffin makes a composite replacement floor. But, from what I've read online, getting it delivered is a problem. I'm going to call and see.

You have to wonder when it occurred to Tiffin that Nova-deck ( the euphemism the mobile home industry found for particle board so buyers might be fooled) might not be a great idea for a “wet” bay. Wet and particle board don’t make for a great combo anywhere.
Meantime, if you can seal seams and flanges on an RV roof you can seal a seam in a floor. Definitely though, the damaged particle board has to come out.

 

[oldwildman]

Yeah, the only kind of good use for particle board that I've seen is a base for formica. But only because of the dimensional stability. Water is still an issue at times. I guess as long as it has a good chance of making it past the warranty period, they don't care

The problem with seaming this problem is that the main seam would be under the front of the freshwater tank. I'd have to pull it anyway. The water pump and basin under the drains are in the same area. And, the supports for the waste tank fall in that same area. No structure under the floor except at the perimeter. Too many points of failure. While I'm tempted to try, I really don't want to tackle this problem twice. We're thinking we'll hopefully using this unit for 8-10 years. And, while it will be a chore to do it right this time, it will be even worse if I have to do it again when I'm older.

 

[rvlifer]

You have to wonder when it occurred to Tiffin that Nova-deck ( the euphemism the mobile home industry found for particle board so buyers might be fooled) might not be a great idea for a “wet” bay. Wet and particle board don’t make for a great combo anywhere.

I dont know if this is a different problem but as of 2022 they still seem to be having some trouble with holding tanks

https://www.rvtravel.com/tiffin-rv-recall-water-tank-drop-exhaust-pipe/

 

[Professor David]

I watched to video too. Looks like quite an operation. Doable but not without some bad curse words. I agree that after all that work...I would NOT feel good about putting particle board back in a wet area.