Saturday, September 30, 2017


All I can say about this post is, crap.
Do yourself a big favor:  Don't Google the phrase "toilet meme". 
This gets Un-Fun Blog Post of the Year Award, so I'll keep it short and not-so-sweet.

On our way back from Canada a few weeks ago, we started noticing abnormal odors from the wet bath.  By the time we got to Houston and were moving the van into storage, not only were there odors, but small trails of water were snaking their way across the center hallway from beneath the cabinetry adjacent to the wet bath.  Another repair was clearly indicated, but initially it wasn't clear whether the toilet or the plumbing and black tank system were involved in the breach.  Here were the steps involved in resolving this.

(1) The first thing I did was flush the black tank better than it has ever been done before.  I musta ran 50 gallons through that thing.

(2) My husband de-installed the existing toilet, which was a Thetford Aqua Magic V.
That's the hole cut in the wet bath enclosure, and the black tank beneath it. 
The plywood edge should not have been left raw like what is shown above, so I sealed it with oil-based enamel paint, which just happened to have been red. 
(3) I then inspected the black tank thoroughly using both my iPhone, which I shoved in there to take pictures (it was clean), and we also bought an endoscope, which I ran to the dump line from above and from below.  The black tank in this model of Airstream Interstate is very tabular.  It is only a few inches high, but it must be four feet long, extending under the wet bath, under the refrigerator / microwave cabinetry, and all the way back to our lithium battery bank (in fact, the black tank holds up a couple of our peripheral electrical components).

I could see no evidence of damage or breach, so we moved on to the next step, which was to fill the black tank very full of clean water, and cap it so that we could take a test drive and slosh it around really well, to see if any water emerged.
This common 3-inch drain plug is available at any big box hardware store.
(4) No water emerged from the slosh test.  We therefore concluded that the Thetford was the only source of our problems.

Ah, the Thetford. What an extraordinary piece of crap. Never have I seen a worse design in the entire universe of RV products, and I'm not the only person who feels that way.  Almost simultaneously with our troubles, Roadtrek Life published this post describing his troubles with the Thetford, of which he reportedly had purchased three inside of six years (!).  Wisely giving up on the model entirely, he replaced it with a Dometic 300, but not before explicitly showing what is so horribly wrong with the Thetford.
The internal body of the Thetford, the space between the bowl and the outer wall, is fully open to the black tank.  Black water sloshes up into there due to road bumpiness and when you slam on your brakes.  And it deposits waste inside the body of the toilet, if you can believe that.
 At first I didn't totally register what Roadtrek Life was saying.  Frankly it was too horrible and too stupid a design to even contemplate.  Just as I had trouble comprehending it, so too did the readers of Air Forums (this thread) when I politely attempted to describe what was happening.

I finally got it when I visually examined our own Thetford.  And then I performed this test.
I turned the de-installed Thetford upside down on a step stool, filled that interstitial space full of water, and left it overnight.  And this happened.
Not only does Thetford's design allow black water to slosh up into the body of the toilet, the body of the toilet is not waterproof.  The hose water steadily leaked out onto the ground, as you can see here.  So apparently, it's only a matter of time before you'll have odors and then black water leakage with that model of toilet.

This image above does not show a toilet, but it represents an analogous problem. Except the space suit helmet is air and water tight, unlike the Thetford. 
(5) The question then became, what do we replace this disgraceful Thetford with?  I called my marine wholesaler contact and asked for advice (I'd bought our Vitrifrigo fridge from him).  For a simple gravity toilet, he recommended the SeaLand 500 series, hands down (SeaLand was acquired by Dometic so the terms tend to be used interchangeably).  He noted, however, that many smaller RV and boat baths have insufficient room for mounting a 500 series toilet (PDF with specs and instructions here), and that did prove to be the case with our wet bath.  Therefore, we were stuck with the cheaper 300 series, specifically the 311 (Roadtrek Life had even less space than we did, and reportedly installed the 300).
This is a view of the underside of the Dometic 310/311 (I can't get full clarity on those model numbers), and my finger is pointing toward a plastic shield that the Thetford lacks.  That's what stops black water from penetrating the full body of this toilet model.  Compare to Roadtrek Life's annotated Thetford pic above. 
The Dometic 311 fit our available space, but it is not the quality that I'd hoped for.  Multiple reviews report that the 310 and 311 tend to develop leaks at the seam between the porcelain bowl and the plastic base (e.g., see reviews at Amazon).  But given our fit constraints, we couldn't find a better, higher-quality choice.
^^ This is what I was feeling like when I was reading low-ended gravity toilet reviews.  No model was reported to be free of problems. 
Furthermore, the Dometic 311 is not the dimensions I'd prefer in a perfect world.
You can see how close the rear hinge is to the back wall.  There's no way we could get a larger and more expensive toilet model in this space.  But that's not the only size issue - it's not as short as I would prefer, either. 
It's slightly higher than the Thetford.  At 5'6", I'm taller than the average American woman, but even I can't place my feet on the floor when I'm sitting on this thing.  That's not a comfort issue so much as it is a durability issue.  I know that this is not necessarily recommended, but my husband and I use the toilet when our rig in underway at highway speeds (we drive up to 760 miles a day - using the head on the fly is a necessary evil under those conditions).  Now that we know how cheaply made all of the available fit-able gravity toilets are, what I'd prefer to do is not put my full weight on the seat while the rig is in motion, lest we hit a pavement crater and start slamming around.  My weight on the toilet at that point would almost certainly add to wear and tear stresses and shorten its already-suspect lifespan.  But if I can't reach the floor, then I can't easily take most of my weight off the seat.

Sigh.  What a pain.  If we go to all this trouble and spend the money, it sure would be nice to have a problem solved long-term, and a reliable outcome at the end of a project such as this.  I don't think that this model of toilet represents an auspicious completion, but at least it's an improvement over that God-awful Thetford, for the time being.

I like to keep my neighbors guessing.  "Um, did she just put a giant stuffed bear on the van toilet...?"   Yyyyyeah.


  1. I did same water test on mine and it did not took overnight to empty the water, it leaks bad around the flusher arm seal. It is hard to really visualize the problem with the toilet design so I added toilet cut-out illustrations to my blog post to better illustrate Aqua-Magic V design flaws.
    PS: I like the huge stuffed bear sitting on the toilet, my daughter has similar but bigger bear that she keeps on her bed :-).

  2. Following InterBlog down the road, now it's time for a new toilet for us too. I gotta say, this blog post is a bit disheartening in that you did not find the toilet of your dreams. If anyone could find it...

    Our Thetford Aqua Magic developed a leak in the back, turned out it was the toilet valve, not the line going to it. Easy to trouble shoot: replace the water line going to the toilet, still leaks (good thing the toilet is in the shower!), must be the toilet water valve. It's seems to be a common problem.

    The water valve on the Thetford is a replaceable part. But given the information found here and in other posts to AirForums by InterBlog, and her research and finding posts by Roadtrekker, showing the short comings of the Aqua Magic, I decided to go with the Dometic 300 series also. Part of my decision was guided by the fact that I had recently replaced the 40 yo Thetford in our Airstream Sovereign, so I was already familiar with the install.

    So, that's what I'm doing, shopping for a Dometic 311. If anyone has more recent info about a more desirable model/make, I'd like to know about it.

    Thanks, again InterBlog, and Roadtrekker for sharing your valuable experience.