Dear Dave,
The wood under the toilet in my RV is soft and the brown tank is falling. Help? —Frank, 2003 Jayco
Dear Frank,
The wood you are describing is most likely 1/2” or 5/8” plywood that is the subfloor in the design. To save money, some RV manufacturers use chip board or even particle board, both of which get soft and break down when moisture is present.
Here is the floor under the toilet of a 2003 Winnebago Brave. We upgraded the toilet to a taller, porcelain model. You can see the wood underneath the vinyl covering.
Soft floor
If the floor is soft, I would assume there is a leak somewhere from either the toilet or the supply line making the wood soft. You will need to remove the toilet to find out where the issue is. Then, cut out the bad wood and try to find the floor joists. You should be able to see them from the underside. Here is the floor torn off a Salem that had a moisture leak.
You may need to replace some of the joists. Or you may be able to add some “sister joists” fastened to the existing ones to reinforce them and give you more footprint or support for the new floor.
Black tank falling
I would assume that you are referring to the black water tank, which would be the one directly underneath the toilet to hold sewage. This could either be soft or rotten underneath support or the straps commonly used to hold in under the floor are loosening. We have had several readers with a similar situation.
Most of these are held in place with straps or metal braces and some cover them with the corrugated plastic underbelly like this one. You should be able to reinforce this.
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RVDT2785
The biggest problem with a soft bathroom floor? Finding a mobile RV tech willing to tackle the project. Our trailer is stationary and used as a winter home. No lack of mobile RV techs in Texas Hill Country, but almost none will tackle infrastructure problems.
Getting this rig into a shop is a huge effort. We have to restore collision coverage, remove the bespoke PVC sewer line (knowing even a couple inches difference when returning can be expensive plumbing work), moving our stuff and pets into an alternate lodging, and hiring somebody to move the trailer both ways as we sold the truck because we didn’t need it.
Won’t call the floor replacement minor, but would be the smallest part.