Sunday, December 4, 2022


Ask Dave: My toilet and tank opening overlap. This is not good!


Dear Dave,
When I open and look down into the toilet, I see a round hole in the toilet that does not line up with the round hole in the tank (or tank pipe). Hard to describe, but it looks like two circles that are offset from one another. The two openings overlap, which creates a small shelf where solid material likes to congregate. I cannot figure out how the toilet is mounted. There is no visible mounting hardware. It is down too far for me to cut away some material, but I’m not sure if I would be damaging the toilet or the holding tank. I think I have to remove the toilet and remount it in a new position but can’t figure out how to do this. Any help would be appreciated. THANK YOU! —Stas, 2004 Fleetwood Tioga Model 23E

Dear Stas,
My first question is, how long have you owned this unit? Since it is a 2004, it’s almost 20 years old. Nobody noticed this before?

Nevertheless, here is a 3D drawing from a similar Winnebago Class C from their site. It shows what the typical Class C unit has for a toilet to black water tank connection.

The toilet is connected at the floor to a toilet flange, or sometimes referred to as a closet flange. There should be two bolts coming up like in the photo below that are fastened with nuts. There may be a decorative shroud around the bottom that you need to take off to get access to the nuts.

You can see the lower pipe that has been attached to the rubber grommet on the black water tank that looks like this.

Possible causes

There are a few things that could have happened in your case. The first would be someone at the factory “goofed” and cut the hole in the floor a little off. I doubt it was a miscue in the tank as they are typically cut in a jig and assembled prior to getting to the line. Several manufacturers just “eyeball” assembly. It doesn’t take much to offset the flange with the hole in the tank.

Another issue could be that the tank has moved slightly. Most black water tanks are mounted with holding straps rather than sitting on a solid floor. Since this is a Class C with little or no basement, I would imagine it is suspended with straps. Sometimes they just stretch a little, enough for the tank to drop slightly and the pipe to come out. If this happens, it would not be uncommon for the tank to shift slightly and cause this effect.

Check the black tank

I would check to see if you can get access to the black tank and verify if it is loose or firm. Typically Fleetwood installed the tanks in the center of the chassis rails, so look underneath and see what access you have.

Another option would be to get a 2×4 and cut it down to 3” wide and drop it down the hole and see if you can pry the lower hole over slightly. This will verify the drop of the tank.

I would not try cutting either of the holes to try to align it as you will have a gap. That would not only get smells coming up, which I assume you already have, but would also allow sewage to drop down into the gap.

I would suggest taking the toilet off so you can get a good look at the floor flange opening and lower pipe or tank gasket. If you do not see the gasket, my guess is the tank shifted and the gasket dropped in the tank or outside. If you can’t move the lower pipe or opening, then I would look at getting an offset floor flange that comes down and angles slightly, which could match the tank hole.

 You might also enjoy this from Dave 

Can I move my RV’s toilet?

Dear Dave,
I want to remodel my RV’s bathroom, which would include moving the toilet. It would still be above the holding tank but I would need to put the fitting in a different location. Is there a way to install a new fitting in the tank? I would plug or cap (whichever is appropriate) the existing one. —Dave, 2000 Southwind 34N

Read Dave’s answer.

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here


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Barb Kimmich
16 days ago

We had a 2003 Tioga 31w for 4 years – sold it a month ago when we upgraded to a 2009 Pace Arrow (vacuflush system – whole other animal). However as I recall, our Tioga looked “offset” as well when you looked down the hole. If we used enough water when flushing we never had an issue.

Sandi Pearson
16 days ago

Our toilet is offset from the hole as well. If you keep the valve shut until dumping…there is no problem with congregating on the shelf. Dump, rinse, and dump. Stating as he did sounds like he keeps his valve open and expects things to fall down the hole directly..not collecting on “the shelf” did I miss read/ misunderstand? In 20 years seems like someone else would have corrected it, if it were a problem.

Dave Engstrand
17 days ago

Ours does not go straight down to the tank, there are two 45° elbows. Is that a possibility in that one?

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