… Toilet Swap — Fostering Adventure

TOilet Swap

Breaking the tether

The original toilet was very nice, but used a lot of water to function.

Although we selected the original Thetford Tecma toilet for the build out of necessity, we weren’t aware at the time just how much water it used for each flush. We had to use this kind of toilet because, unlike regular RV builds, our black tank couldn’t be placed below the toilet because of the rear wheels underneath. We chose the Tecma because it’s macerating function can pump the effluent to wherever the black tank has to be placed. It’s high water use wasn’t an issue for our supply, you understand. After all, we carry nearly 200 gallons of fresh water. The problem, however, is the speed at which the toilet fills the black tank.

Unlike our Class A motorhome that could last three weeks before it needed dumping, the same size tank in our truck barely lasts a week to ten days. This meant we always had to be looking for dump stations. Which can be an issue, particularly in northern Canada during the winter when everything outside is frozen. This dump station necessity also presents a problem if traveling overseas was ever to take place. Dump stations are a North American invention, and not ubiquitous around the world. That’s why cassette toilets are so often installed in world travel vehicles. They can be dumped just about anywhere there is an appliance connected to a sewer… a regular toilet, outhouse or other similar situation. The problem is how often it has to be done, every two or three days. This is why we didn’t want a cassette toilet in our rig.

Since we needed a way to untether the truck from dump stations, and didn’t want a cassette toilet, the remaining option is a composting toilet. Vehicle installed composting toilets were in their infancy when we were designing our truck, and there weren’t a lot of options at that point. Fortunately, things in that regard have changed.

choOsing a composting toilet

Nature’s Head

Air Head

We’ve been looking at composting toilets for some time. For vehicle use, the most popular ones in North America seem to be either the Nature’s Head toilet or the Air Head toilet.

The two toilets are virtually the same, with the Air Head having a slight advantage when it comes to emptying the toilet. But both toilets have to be disassembled, and the bottom half removed in order to empty it. Something that’s particularly awkward in the tight confines of an overland vehicle bathroom.

The other characteristic that the two toilets have in common is their manner of manufacture. They’re both made from a type of plastic that’s not particularly attractive. In fact, both units are in our opinion, very industrial looking and their complex construction makes cleaning them a real chore.

Compoost toilet, A Much Better alternative

The Compoost Toilet

In our search for a better option to the above mentioned products, a video from Swiss/German overlanders Christian and Sybil Hütwohl (Benny-Goes-Overland.com) introduced us to a toilet made in the United Kingdom. After corresponding with Christian, and learning the toilet manufacturer was no more, we started searching for other alternatives in the U.K. and Europe. This yielded a new-ish company, Compoost Toilets, located in the U.K. town of Rugby. (compoosttoilets.com)

Their product is, in our opinion, superior to the American products in a number of ways.

First off, it’s infinitely better looking. The body is a fiberglass one-piece unit with a finely finished high gloss exterior very similar to porcelain. It also has a proper, removable Euro-style toilet seat and cover.

Secondly, the toilet bowl/urine separator is also a highly finished one-piece fiberglass casting which is attractive and easy to clean.

Thirdly, and perhaps most important of all, what makes this product so much better than the others is how it’s emptied. Instead of having to undue multiple screws and dismantle the toilet so half of it can be taken outside to empty and clean, one simply raises the hinged toilet bowl/urine collector at the front to lift out the urine bottle or solids bucket. That’s it. The main toilet assembly remains unaltered and firmly attached to the floor of the bathroom. The toilet seat and lid are also easily cleaned as the push of a single button allows them to be removed from the toilet body.

A Compoost toilet with self-stirring solids bucket and piped away urine collection.

The other big advantage of the Compoost toilet is that it can be purchased for use with a conventional urine bottle, or for use with the urine collector hard plumbed into a urine tank. Since we already have a black tank that we’ll repurpose as a urine tank, this is the model that we bought.

The final improvement of this toilet over the competition is that one doesn’t have to hand crank a mixing paddle to agitate the solids with the compost media. Instead, it has an inconspicuous little button on the side of the body that activates an electric stir motor to do the job.

The Conversion Process Begins

The old toilet was a complicated device with a lot of electronic and plumbing connections.

To convert to a composting toilet we first had to remove the old toilet and the plinth it was mounted on that accommodated the plumbing system. The toilet came out easily, but the plinth was another thing entirely.

After removing the toilet, the plinth itself couldn’t simply be unbolted and lifted out. The fasteners that held it in place were covered by the ceramic floor tile. So to get at them, all the tile had to be chipped away. But once the fasteners were removed, the plinth still couldn’t be lifted out. Other things that were installed after the plinth still keyed the plinth in place. So instead of removing those other items, such as the wall bolsters and bathroom cabinet, we removed the plinth by cutting it into small enough pieces that it could be pulled out one bit at a time.

The builder used grossly oversized piping to hook the toilet to the black tank. It’s twice the size of the piping inside the toilet. How stupid is that?!

The toilet plinth appears to have been built in place. The only way to remove it was to demolish it. Here I’m making the first cut.

Removing the piece that joins the left side to the right.

The floor tile was installed after the plinth was screwed down, so the tile had to be lifted first to get to the screws.

A flat pry bar was used to drive under the tile to lift it off.

All of the tiles had to be removed to get the plinth out.

Finally the last piece comes out.

They certainly used enough wood for this plinth.

With the plinth gone, the floor was cleaned and the in-floor heating pipes were properly put back into the floor slots.

Pre-mixed mastic was used to secure the new tile. We had bought extras for just such a need.

Using spacers and tape, the tiles were held in place while the mastic cured.

All finished with the grout installed and dried. We had some of the builders grout left over that we saved.

Custom Modifications to the CompoOst Toilet

Some of the parts we bought to modify the toilet for our installation.

Although the Compoost toilet is dramatically better than the alternatives we looked at, there were a few things that we wanted to do to it so it would fit our installation better. Since we now had two waste water storage tanks, we wanted a way to divert the liquid outflow from the toilet to one or the other tank. We also had to alter the toilet to accommodate the plumbing pipes running along the floor behind the toilet.

The only other thing we did to the toilet to improve it for our use was to take advantage of our existing, solenoid activated water source from the old toilet to provide water to a spritzer spray nozzle we installed in the urine bowl to easily rinse it after use. This prevents urine residue, and the associated odor, from building up after use.

This is the fluid outflow collector before modification.

A 3-way “T” valve was installed to divert fluid between two tanks.

The collector shape required two 45° elbows to configure the flow direction.

The 3-way valve handle was altered so the direction of flow could be known. This position sends the fluid to the front tank.

This handle position diverts the flow to the rear tank.

The completed diverter with the two 3/4” hose barbs for the plumbing lines.

Fresh Air Circulation

The cabin is so airtight that air has been pulled into it through this boiler tube port that goes to the exterior boiler compartment. The port was improperly sealed by the box builder, so dust has also entered the cabin along with the air. This was … — The cabin is so airtight that air has been pulled into it through this boiler tube port that goes to the exterior boiler compartment. The port was improperly sealed by the box builder, so dust has also entered the cabin along with the air. This was corrected when we cut in the fresh air ingress port.

In order for composting to work, fresh air is needed for the decomposition process to take place. In a composting toilet a fan is used to pull fresh air through the composting chamber. This fan runs constantly, as long as the composting chamber has material in it, and also provides the secondary function of removing odors from the toilet and expelling them outside.

In our installation, this air circulation presented a small challenge. When our cabin is closed up with all the windows, doors and exhaust fan hatches closed, it’s close to a hermetically sealed enclosure. The toilet fan is very small and as such is not powerful enough to pull air in through the various seals in the doors and windows. So this prevents air from entering the cabin to replace the air that the fan is trying to draw out of the toilet. Aside from this interrupting the composting process, it would also allow odors from the toilet to infiltrate the cabin.

For our installation to work, especially in cold temperatures when the cabin would be closed up, we had to find a way to let air into the cabin unimpeded. In wintertime, this presented the added complication of pulling frigid air inside. Something that we wanted to avoid as it degrades the comfort of the living space. Luckily, the location of our boilers provides us with a viable solution. Since both boilers are housed in the storage compartments underneath the cabin, and the pipes from them enter the cabin through the floor of the under bed storage area, we could use this to our advantage. Those pipes, once inside the cabin, run through a tunnel on the floor along the passenger side wall. By cutting an air ingress port in the floor inside this tunnel, the incoming air would be warmed by the heating pipes as they both travel the length of the six foot long tunnel.

Correcting the builders improper work

When the builder plumbed the truck, the lines that enter through the floor of the cabin from the boiler box below were not properly sealed. They used a simple brush style circular screen which doesn’t stop dust infiltration, and probably wouldn’t even stop insects from gaining access to the interior of the truck. Just what their installation was meant to do is a mystery to us. We removed it and injected proper urethane foam insulation to totally seal off the five inch diameter hole.

This shows all the dirt being pulled into the cabin through the boiler tube port. We have to fix this.

Simple urethane spray foam is a much better solution than the builders attempt.

Once the foam had cured overnight we were able to trim off the excess with a knife.

All finished, the foam not only seals the hole completely, but also provides support for the heating pipes.

Cutting In The Fresh Air Port

We needed a proper fresh air port to allow for the continuous operation of the toilet exhaust fan to function. So we cut one into the floor in the rear storage compartment where the incoming air would be preheated before entering the living enclosure.

The location of the air ingress port had to be carefully located as there were cross rails underneath from the steel subframe.

The floor is 3” thick, and we cut it with a standard 3” diameter hole saw.

The floor is made of multiple layers of plywood with a 3/4” thick layer of foam insulation to act as a thermal break.

The port was lined with a piece of PVC pipe which was siliconed in place.

To protect against dust and insect infiltration, a replaceable gauze filter and stainless steel mesh guard were installed.

The filters are easily replaced by removing three screws.

Closing In The Heating Pipe Tunnel

To ensure that the only air pulled into the living enclosure came from outside via our desired route, we fully enclosed the pathway where the air traveled.

We used a block of 2” thick closed cell foam to close off the end of the tunnel so the only air entering it will be from the fresh air port.

We installed an access cover onto the tunnel shroud so we could easily check the status of the ingress filter.

The access didn’t end up centered because we had to miss the steel frame rails under the cabin. Too bad.

The access port has a screw on cover so it is dust and water proof.

We cut out the webs between the pipes to increase the open area for the incoming air to pass through the wall into the living area.

Since the tunnel shroud didn’t go all the way to the wall we had to make some cover plates from plastic to close it in.

Because of all the pipes, we had to also use some foam to plug the gaps around them.

The side cover plate screwed on.

The top plate screwed on. You can see how carefully we fitted the panel to all the various shapes.

Toilet Venting: Completing The Roof Exhaust Stack

The exhaust stack for the toilet vent, although not a difficult installation, did have its challenge. The route took it up inside the two walls that make up the slot for the sliding pocket door, and that pocket is only 1-3/4” wide. Since the vent pipe is 1-5/8” in diameter, that only leaves 1/8” of clearance. The installation required that the hole in the roof be drilled from above, so very careful measuring had to be done so the proper hole location on the roof could be identified.

The easiest way to connect the fan (black part) to the vertical stack was by adapting some electrical conduit parts (grey items).

Simple electrical tape was wrapped around the grey conduit to enlarge it to create a tight fit inside the fan housing.

The hole location dimensions were transferred along the inside wall to the window glass, then out the glass to the outside wall, up to the roof and then over to the right spot.

A pilot hole was drilled first with a guide block to ensure a perfectly vertical hole. We then looked up inside the door pocket to verify the hole went through the middle of the door track.

Next a slightly oversized hole saw was used to bore the hole for the stack pipe.

The hole saw wasn’t long enough to bore the hole in one go, so we had to pull out the first portion and then drill some more.

The second drill stopped as it hit the aluminum door extrusion and that part of the hole was also removed.

The hole remnant had to be picked out with some needle nosed pliers as it was still glued to the extrusion.

This shows just how good our measuring was. The hole is exactly centered on the extrusion.

The extrusion is glued and screwed to the underside of the roof, but cutting the extrusion leaves the extrusion with no screws at the end. So we needed to add one before cutting through the extrusion.

After drilling a hole through the roof underside layer and the extrusion, a self tapping machine screw was threaded in to ensure the glue between the extrusion and roof stayed stuck.

This shows the removed pieces and the tools used.

The hole saw wasn’t quite long enough to cut all the way through the extrusion, so the last 1/8” had to be cut with a hacksaw blade.

The exit port was made from a plastic electrical box which was bored for the stack and sealed to the roof with silicone.

Holes were drilled so screws could be installed for secure fastening to the roof.

Masking tape was used so a clean line is created when the silicone is smoothed on the outside of the box. Screws and pipe were also sealed with silicone inside the box.

1-1/4” PVC electrical conduit was used for the exhaust stack. It was the only plastic pipe size that would fit inside the two walls.

A wire sink strainer was used as an insect ingress shield.

The stack pipe was cut to a precise dimension above the box so the screen would be slightly squished when the lid was screwed on. This prevents any chance that bugs can get in.

The finished installation is covered by the solar panel when it’s put back in place and this prevents any water ingress.

You can see the vertical stack pipe inside the transition box. The odd angle cut on the pipe end was so it could be fed into the box hole while looking down inside the pipe from above.

We used my father’s old bee hive smoker to provide a smoke source to blow through the exhaust stack. The smoker has been sitting on a book shelf in our house from when Dad passed over 20 years.

Feeding the smoke into the fan so we can hopefully see how well the fan draws and pushes it outside.

Hooray! The smoke is quite visible coming out from underneath the solar panels and roof side rails. We feel quite confident the toilet will be adequately ventilated.

Creating the Replacement plumbing covers

Although we were able to completely repair the floor with original tiles left over from the camper build, we still had the problem of the laundry plumbing running along the floor at the back wall of the toilet. This meant that we couldn’t completely eliminate the plinth that was used to support the original flush toilet, and which hid all the plumbing. So two new partial “plinths” were made to just hide the laundry plumbing. They were held in place on each side of the toilet by supports on the back wall and a little silicone to keep them from shifting about.

Since we had plumbing pipes running along the back wall at floor level, we had to create covers on each side of the toilet to hide them.

We used 12mm plywood and glued the floor tile to them to match the floor.

Standard pre-mixed mastic was used for glue. This is before spreading it out with grooved trowel.

The front edges of the tiles were mitred so we could avoid the bulky edge extrusion commonly used.

Once the mastic had set we were able to grout the tiles using the left over pre-mixed grout from the build, now six years old. Really lucky.

The front mitred joint turned out well despite a cut with diamond wheel on a disk grinder.

PrEparing the toilet tub

After waiting months for the replacement parts that were damaged in shipping, no fault of Compoost Toilets mind you, we finally had what we needed to finish the installation. The insurance company made it very difficult for Compoost to complete the claim, and we don’t really know that the claim was ever approved. Nevertheless, Compoost sent us the parts at no charge, including shipping, since we had waited so long. They’re a really class act, and we highly recommend them.

To make it easier for Compoost, we had them just ship us a standard tub without any of the modifications they did for us to account for our unique installation. So those modifications were done by us this time.

The replacement tub and buckets as they were pulled from the cardboard and wood crate.

The original shipment was dropped, so the buckets stored inside were damaged. They were both replaced.

The inside of the tub set up for a standard installation, so holes on each side had to be drilled to accommodate our plumbing pipes.

The rear shelf supports, shown here on the bottom, had to be partially removed because our plumbing pipes ran tight along the wall.

After the two slots were cut into the shelf supports, we painted them with colour matched paint for a professional looking job.

We covered the outside of the tub with masking tape so there would be no damage to the glossy outside surface during installation.

We also had to drill in the second switch that would be used to activate the spritzer valve.

From the outside, one switch activates the stir motor for the solids bucket, the other turns the water flow on for the spritzer jet which rinses the urine collector.

All finished and ready for final installation.

Tub Installation & final assembly

The tub installation was not difficult, but it was a bit tricky. We had to cut the laundry plumbing pipes in just the right spot so one side could be pried out from the wall and the tub slid sideways over them from the right. Then once the tub was all the way to the left, the other half of the pipes could be pried out and then the tub slid sideways to the right until the pipe joints were inside the tub, and the tub positioned at the final mounting position. Then it was just a matter of reconnecting the pipes and hooking up the electrical that powers the stir motor and spritzer valve.

The toilet sits to one side to accommodate the opening drawer, and be centred under the bathroom window.

The result of the toilet being offset to the right meant that the joints for the laundry water pipes ended up off centre inside the toilet.

The laundry drain pipe and the toilet wiring also had to be reconnected through the toilet tub.

When the wiring harness for the toilet was pulled inside the tub, it looks quite complicated. But there's really only three connections to be made. The wires were shortened as needed.

This shows the laundry drain (white) and the drain to the former black tank that will also be reconnected.

With the toilet tub located correctly, we needed to test fit the floor covers to ensure they were sized correctly.

The right side closure needed to be trimmed a bit so it would slide by the toe kick on the side wall.

The toilet tub was fastened to the wall with four screws, and was also siliconed to the floor for a really secure attachment.

The laundry water pipes were reconnected with PEX connectors.

A "T" was installed into the laundry drain line for the alternate urine discharge tube. A rubber connector was then used to complete the laundry reconnect.

This shows the reconnection of the laundry drain, black tank drain and roof vent.

The slip joint for the roof vent was sealed with aluminum duct tape.

The stir motor was re-installed, but had to be clocked 180º to its normal position to accommodate the placement of the exhaust fan.

The toilet spill floor was installed and then the urine drain hose was connected to the "T" and the black tank drain.

We had to install the tub seal, as it didn't come pre-installed like the first tub.

The seal had self adhesive tape on it, so the install was quite easy.

We masked the floor and tub side to apply the silicone material.

Getting the silicone on the right side was difficult as the gap was too small to get in with the caulking gun. We had to apply to a finger, and then smear onto the joint.

The only part of the caulked joint that would be easily seen was the curve around the front of the tub.

The joint was kept small so it was barely visible.

The last hookup: connecting the rinse jet

The important addition that we added to the composting toilet was the installation of a water jet for rinsing the urine collection bowl. Since we had a switch operated water source from the original flush toilet, it was a relatively easy process to add a spritzer jet so the bowl could be easily rinsed after each use. The water jet itself was simply a windshield washer jet bought from Amazon, and then connected with a flexible 3mm hose. A simple press on the side mounted switch button and the spray jet rinses the entire bowl. It’s a great upgrade to a terrific composting toilet, and eliminates the need of a spray bottle to rinse the urine bowl.

The hardest part of installing the spray jet was figuring out where to put it. Trying to determine the spray pattern when there's no hole to put it in takes some imagination.

Once we established the location it was a simple matter of drilling the hole.

Masking tape was used to drill through so as not to chip the bowls finish.

Once installed, the spray jet looked like it was a factory installed component.

The spray jet provided a powerful rinse action that continued as long as the push button was held down.

The water supply hose was routed so as not to interfere with the solids pail or the lid lift action.

The finished install with the chamber lid closed and the toilet seat up.

Toilet seat down.

Toilet seat lid down.

A very clean and aesthetically pleasing finished product.

A longer than expected Project with a successful outcome

A project that we figured would last about a month, from the ordering of the composting toilet to the final completion, ended up taking six months.

This wasn’t because it was a difficult retrofit, you understand, but rather because it was a colossal failure by the shipment carrier. They “lost” the parcel in their UK warehouse for the better part of a month, and when we finally received it there was damage to the toilet exterior as well as some of the components inside. The carton had to have been dropped on its side from a considerable height.

The next four months was filled with the toilet manufacturer trying to get the insurance adjuster to accept the claim and pay for the replacement components and shipping. Whether the claim was ever approved, we never found out. Nevertheless, the manufacturer did eventually send all the replacement components we needed to finish the installation, and with no charge to us for the parts or the shipping. It was very good of them to look after us so well.

The end result was a retrofit that looks like an original installation.