Fifty years ago, a major RV supplier pitched a way for camper owners to easily empty their rigs’ black tanks. Why deal with the sometimes messy and smelly process of dumping your tank when your motorhome’s or tow vehicle’s engine could do it for you? The Thetford Thermasan Waste Destruction System emptied your tank by taking your poopy water and spraying it into your RV’s exhaust manifold, burning it in your exhaust. This is a real thing that existed, and you can sort of buy something similar today.
Last week we had a chat with Bring A Trailer Co-Founder Randy Nonnenberg on our podcast. In it, Randy, Beau, Jason, and David talked about the coolest vehicles to ever roll across the virtual Bring a Trailer auction floor. One of them was an epic 1972 Ford Condor II motorhome that once belonged to McLaren Engines chairman and CEO of McLaren Racing Zak Brown. The RV itself is pretty cool, or baller, as the kids would say.
But readers had a question about this paragraph in the Bring a Trailer listing:
The kitchen area includes a refrigerator, freezer, pantry, and a kitchenette with a single-basin sink, oven, stovetop, and wood cabinets. The adjacent bathroom is equipped with a Thermasan waste destruction system that was designed to dispose of liquid and organic waste materials through the exhaust system.
You read that right. This vintage RV is equipped with a system that takes the liquids of your black tank and “disposes” of them in your RV’s exhaust stream. But how did it work? And what happened to them?
[Editor’s Note: I’m going to start saying “evacuate my holding tank” whenever I take my bowels for a spin now. – JT]
Alternative Methods Of Dealing With Your Crap
The idea of dealing with human waste in vehicles goes back about as far as the RV itself does. However, back then, somewhat similar to how it is today, dealing with human waste often involved filling up a portable toilet and dumping it later on. It’s hard to say when inventors began to consider burning up waste, but the seeds of the Thermasan system were planted in 1931 and 1948, respectively.
In U.S. Patent US1892132, published in 1932, inventor John L. Berney shows off an atomizing system fitted to an airplane’s exhaust. This system is designed to atomize pesticides in an airplane’s exhaust, leading to the pesticide landing on crops. And in U.S. Patent US2658202A, applied for in 1948 and published in 1953, inventors Abel Wolman and William A Hazlett created a system for a vehicle to dispose of human waste.
In this system, wastes would go straight from a toilet and into a grinding machine or macerating machine. Once the waste is ground into small particles, they would go into a holding tank. The waste would then flow into a heating chamber, where the waste would be disinfected through a heating process. Once the waste particles are heated to 170 degrees and once the vehicle reaches a determined speed, a valve opens, disposing the apparently disinfected waste onto the ground. The inventors note that dumping heated poop particles onto the road might be unsightly, so it’s designed to spread the discharge out.
The Thetford Corporation–a company known for RV plumbing products–would reference these patents, as well as a 1961 patent from Airstream for a toilet that burns waste, when it would patent the Thermasan Waste Destruction System. The Thermasan effectively combined attributes from a number of the aforementioned systems and more into one. In its patent, Thetford reveals that it wasn’t the only company working on a way to burn waste. There was another patent for a a system that burned waste in a drum fitted around an exhaust.
I haven’t been able to pinpoint exactly when the Thermasan system first hit the market. The earliest example that I could find was the 1964 Ford Condor motorhome, which was noted in MotorHome Magazine as having the Thermasan system. Thetford itself was founded just a year before.
How The Thermasan Works
So, how does the Thetford Thermasan Waste Destruction System work? Thankfully, there are brochures and data sheets archived online.
First, you switch on the system. Thermasan will only destroy wastes when the engine is hot enough and when the vehicle is traveling at a high enough speed. When the engine is hot enough and when you’re going at least 30 mph, the system can activate. If conditions are correct, an injection pump will operate that pulls wastes out of the tank. A probe in the tank makes sure that what gets picked up by the pump doesn’t have waste suspension. The pump meters the flow so that not too much liquid is introduced into the exhaust flow. Next, the waste is injected into the exhaust flow at its hottest point, which Thetford says in the brochure should burn the waste up so well that there are no visible discharges from the exhaust or a smell.
How it works in depth is pretty neat, and involves a bunch of parts. A question that you might have is how does this 1960s-era system know when you’re going fast enough, or how the engine is hot enough.
In installation documents, Thetford explains that the system measures speed from a speed sensor installed in-line with your speedometer cable. How that works is that you’d remove the speedometer cable from the transmission, install Thetford’s speed sensor, then install the speedometer cable on top of the sensor. In the installation documents, Thetford warns not to install tighter than finger-tight, warning of the damage that can occur.
A wire then runs from the speed sensor to a plate that contains a vacuum sensor, and then to the control head assembly. When you reach or exceed 30 mph, one condition is met for Thermasan to work.
Next comes what Thetford calls a heat sensor in the brochure, but a vacuum sensor in the installation document. All this sensor is looking for is 16 1/4-inches to 17 inches of vacuum. Thetford expects the vacuum line to be installed on a source originating from the intake manifold. When conditions are met for both vacuum and speed, the system tells you that it’s ready to burn your crap.
There are multiple versions of the Thermasan, and the one you get depends on what kind of equipment that your RV has. There’s a version for RVs that just have a black tank, a version for RVs with a single combined tank, and a version for separate tanks. No matter the version chosen, the person installing the system has to drill into a flat spot on the tank to install the probe. From there, a pump extracts fluids from the tank.
The final part of the system is called the Sanijector. This is supposed to be installed on the hottest part of your exhaust, but after the catalytic converter and before the muffler. For this, you drill into your exhaust pipe, place the Sanijector, and secure it with exhaust clamps.
It seems installation is easy enough for anyone to do. And if you’ve checked the brochure by now, you’ve probably realized that Thetford marketed these for travel trailers, too. How does the system work when your RV doesn’t have an engine? Well, Thermasan systems meant for travel trailers would have a hose bringing the wastes to the exhaust pipe of the tow vehicle to be burned there.
Using The Thermasan
Of course, you’re probably wondering, as I also wonder, how this system works in practice. Sadly, it seems like there aren’t any reviews of how this system works. There are forum posts, but few of the people in them ever actually experienced the system. One person says that the system does such a complete job that you don’t smell anything. Another is a post from nine years ago from someone claiming to be an engineer for the Thermasan. They say that they had to work hard at controlling the system’s injection rate so that their laboratory didn’t smell like a “roasted diaper.”
And in the documentation from Thetford, the company warns that there can be an odor present from the vehicle’s exhaust if the holding tank wasn’t diluted with enough water or a Thetford treatment chemical called Aqua Kem. I shudder thinking about following behind an RV that smells of burning poop.
In addition to that warning, Thetford also says to avoid putting things in the toilet that holds strength in water like facial wipes. Today, I’d imagine that list would also include cleaning wipes and paper towels. The Thermasan system can only burn things that dissolve in water. And amusingly, Thetford tells you not to pour stuff like gasoline into your RV’s black tank.
But if you can live with all of that, Thetford says that your Thermasan Waste Destruction System will turn your RV into a mobile, pollution-free waste destruction plant. And you’ll “join the unhooked generation” as you blow past dumping stations as your engine burns your poop.
This system was marketed for a number of RVs back in those days from Airstreams to the famous GMC Motorhome. It seems that the system was marketed from the mid-1960s to the late-1970s. Then, it appears that the product disappeared from the market. It’s unclear when this happened, and Thetford doesn’t even note the product in its history. I would love to know why these were eventually taken off of the market. I’d also love to know just how many of them were produced.
And if you’ve read all of this and you’re still interested, you can actually buy something like this today. Inventor Namon Nassef made a new interpretation of the Thermasan back in 2011, but it looks Nassef never got the investment to put it to market. You can buy the Incinolet, a toilet made for boats, cabins, basements, trains, and other places where you might not have sewer access. Like the Thermasan, it burns your waste. But instead of using a vehicle exhaust, it does the job on its own.
To answer my questions and more, I reached out to multiple representatives at the Thetford Corporation. After about a week, I haven’t received word back from the representatives. Thus, my research has reached a dead end. If you know anything about this rather interesting system, even if it’s just experience using it, drop me a line at mercedes@theautopian.com.
I suppose this is at least peripherally related to the macerator/chlorinator systems used with marine toilets.
Going further, with enough space you could build a mini sewage treatment plant.
We had an RV that had one of these but it had been disconnected so sadly I cannot comment on how it worked, some rvs have macerator pumps that turn the solid waste into a liquid so it can go through a smaller hose so maybe somebody can reinvent this
Boy, this could add a whole ‘nuther dimension to road raging:
“That guy’s tailgating me! Say hello to last night’s truck-stop chili!”
As a technician, cars can be disgusting enough already due to the human factor involved. Can’t imagine having to replace a shit injector, or a jammed crap grinder.
Good grief, perhaps not the best idea when one takes into consideration that prions can survive conventional incineration & even conventional autoclaving. So the Thermasan method could potentially be spewing all kinds of TSEs (transmissible spongiform encephalopathies) including mad cow disease, kuru, & Creutzfeldt–Jakob disease, all of which have pretty much 100% fatality rates plus they have incubation periods ranging from a couple of years to forty years or so. Thank goodness Thermasan never caught on…
A lot of people don’t know that prions are in the U.S. food supply. Lots of Alzheimers clusters throught the U.S. which are likely improperly diagnosed. In order to diagnose vCJD, the brain of the deceased has to be split open, exposing the researchers to the prions. Then there’s the political issue of the CDC not wanting to discover it, or upset the companies producing the poisoned food. Cramming livestock into massive factory farms and feeding herbivorous ruminants parts of other animals which may or may not have been fed parts of their own dead has consequences.
I’d be much less concerned contracting this disease from exposure to human excrement than I would be from the contaminated food itself. But it is nice to not have to worry about getting shit spray all over oneself for riding a motorcycle, open-wheeled car, bicycle, or similarly exposed conveyance on the public roads because this product never caught on.
An old rhyme on the subject that is applicable: “In ye days of olde, when nights were bolt, and flush toilets were not yet invented, we’d deposit our crap to the side of the road, and saunter away, contented.”
*bold, not bolt. Can’t believe I screwed that up.
This is a great way to eliminate tailgating. I’m not following one of these too closely as a fine mist of cooked shit is not part of what I call a great day.
So Dave Matthew’s crappy tour bus didn’t have a Thermasan. If it had, they wouldn’t have made the news years ago and wouldn’t be in hot water, ie: trouble. They certainly did take a dump though.
If you think about it, if it was just grey water (not black), and a diesel, urea injection before it was a thing.
“DROP me a line at mercedes@theautopian.com” No pun intended.
If only they could have devised a way to siphon off Methane and use it to run a Generator.
So… when you make certain sauces, you leave them on low heat to remove the liquid by evaporation, leaving a concentrated sauce.
I can only imagine the shit reduction left behind in the tank.
Add some flour and butter for an amazing roux.
A lot of composting toilets do just that, except it dries everything completely and a fan ventilates and takes the smell outside via a pipe. You have to leave the seat down or the fan ventilates the interior of the thunderbox instead…
The Ultra Van (Ultra Coach) used them as well.
As for the demise – I’ve read that one contributor was that nefarious types used the system to illegally dispose of hazmat.
This is definitely a system I would *not* work on myself. Someone else can deal with this shit.
I know, right! Maybe if I were installing it on a brand new RV that’s never been pooped in. Otherwise, you can’t pay me to drill into a black tank.
Ok, maybe if I were wearing a hazmat suit. lol
The EPA was created under Nixon, so I’m not surprised this disappeared by 1980. Human waste concentrates heavy metals and other stuff not good for us*,so dispensing it on the highway could be considered illegal disposal of hazardous materials. Selling a product expressly designed to do this seems like a great way to invite serious scrutiny-and possibly major fines. A shitshow, if you will.
*25-30 years ago someone had the idea of roasting human effluent to sterilize it and spreading the results on fields as fertilizer. When this was tried, the resulting product had elevated levels of certain heavy metals and pharmaceuticals: not what we want to grow our foods in.
Thanks for the article, Mercedes: provoked a early guffaw from me. Great way to start the day.
I was wondering if it had something to do with the Clean Air/Clean Water acts, but then she showed that similar products are still produced. Also, I work for a sewer utility (We’re #1 in the #2 business) that uses incinerators, so clearly there is some way to do this that doesn’t run afoul of the EPA.
Plus 1 Internet point for “shitshow”.
Thanks for this. I was thinking there’s probably a good reason we aren’t burning fine mists of shit right now if this was such a great invention
I’ve encountered Incinolets in bush Alaska in contractor camps. Honey buckets (normal 5-gallon buckets) were and are still seen in some villages.
“Set fire to that shit and spread it around” is the usual answer to a messy problem.
Pity the poor technician when the owner comes in with the line to the exhaust blocked…
I mean, I know RVs get shitty mileage, but that’s ridiculous…
Whoa. Idea here. Add methanogenic bacteria to the shitter, then pipe the resulting natural gas into the intake manifold. THe amounts produced would be tiny but you would still be partially running on shit.
Ok first off, that Ford RV is awesome, can’t believe I’ve never seen one before.
Second, great article, this is the kind of weird automotive related stuff I love to read. Keep it coming!
Can’t tell if the Dave Matthews Band bus had one of these or not.
They didn’t. That was the problem!
>[Editor’s Note: I’m going to start saying “evacuate my holding tank” whenever I take my bowels for a spin now. – JT]
Any other Vermonters who may be reading this will know what I mean when I say I’m now calling it “deploying a Malloy”.
Note: no catalytic converters at the time the Thermasan was marketed,
Fascinating product and great write-up, Mercedes. It’s a shame Thetford never responded, although the engineers and others involved in it are no longer there, I’m sure.
Thanks!
Catalytic converters were coming into use at the tail end of this product’s existence. The installation manual itself says to place the injector after the catalyst. No date is printed in the manual, but it’s probably fair to estimate that it was printed in 1975 or later. The best estimate I’ve seen is that the product was discontinued in 1980, but no confirmation of that.
Edit: Honestly? I’m not surprised that I didn’t get a response from Thetford. In the past, when I’ve researched vintage products/vehicles (the Honda Pacific Coast, U-Haul camper trailers, etc.) I only lucked out because there was literally just one person left at the company with knowledge of what I was asking about.
Sometimes I strike out! Another example of this is when I asked Yamaha about my obscure motorcycle, and the rep couldn’t find anyone who worked on the bike back in the ’70s.
Does RV stand for Recreational Vehicle or Rectal eVacuation?
A lot of old cabins in the pacific NW have gas powered toilets (no pun intended). They fire up with the push of a button and burn off your mess over a few minutes. It had a chimney that “dumps” off the outside wall of my cousins cabin. It left and awful sh*t stain on the wall where it exhausted.
Back in the 70’s there was one in an outhouse I used while attending a workshop in Wisconsin. I think it was called a “Destroylet”. Or something like that. It worked great except it made such a racket when you flushed, you had to leave quickly.
I’ve seen a similar system while on vacation in Canada. It was supposed to have a sealed combustion chamber to burn your waste when you were done.
I’ll just say that you had to get out of that outhouse in a hurry for reasons other than the noises it made.
How is Destroylet not a metal band name yet?
I like it! Display an “I heart Thermasan” bumper sticker and deter tailgaters.