[Ran D. St. Clair]

Toilet Tech Talk

My ECOJOHN SR5-P12 arrived about a week ago and I have been studying it carefully. I must say, I am not entirely happy or impressed. If you have been following along, you know that this toilet is the centerpiece of my design. It is the most expensive single item except for the truck itself, and I am taking a bit of a risk buying it sight unseen.

I am determined to make it work because if it doesn’t work then I will have to rethink and redesign many other aspects of the vehicle including electrical power generation. I will be modifying the toilet to suit my needs, which probably implies voiding any warranty.

At this point I can’t recommend the toilet for an RV application. If it ultimately works out OK I may be able to change my tune, but even then it will be with some fairly extensive modifications. Let me start by listing my main issues with the toilet, in rough order of their importance to me.

1. The owners manual and installation instructions range from minimal to very poor. There are a number of parts I received that aren’t mentioned at all. For example, there is no mention of the catalytic converter, and there are various parts probably related to mounting the chimney that I have no idea what to do with.

2. They more or less lied about the toilet running off of 12V. It requires two 12V batteries in series, which last I checked is 24V. Now I will have to install a 2nd 12V power supply that runs off of my inverter to create the 2nd 12V supply. (Correction: Upon further inspection I note that some of the literature does specify two 12V batteries are required, so I guess it's my fault for not realizing that they were going to be in series. They could have just said that though...)

3. Some aspects of the toilet are not very well made. The solder joints relating to some of the wiring are among the worst I have ever seen. I am a manufacturing engineer in the electronics industry so I may have high expectations for this sort of thing, but this is bad by any standard. The spiral metal armor over the high voltage ignition wire had sharp burrs on both ends, inside and out as well.

4. It seems to me that the toilet is not designed for anything other than a fixed point application. The owners manual mentions in passing that it can be used in an RV, but the overall construction is not suited to take the pounding. For example, there is an electrically and pneumatically actuated propane valve that is connected to the unit with a short length of ¼” soft copper pipe. It is mounted in mid air with no mechanical support other than the copper pipe. Any bouncing at all will work harden that copper pipe and cause it to crack over time. Also, the fire box, which is probably 60 pounds, just sits loosely inside the ABS plastic housing. There is nothing to keep it from sliding around except for a light weight sheet metal bracket attached to the auger input, which is not firmly attached to the fire box. I am also concerned that all that weight will eventually crack the ABS housing since it is mounted on 3 legs molded into the housing with no support directly under the firebox. Finally, there is no provision to bolt the thing to the floor.

5. The delivery of the toilet was slow, and when it arrived they forgot to send some of the parts. I had to call them and remind them to send my toilet bowl liners and the all important owners and installation manual. To their credit they sent them right away after I complained, but they weren’t the least bit contrite about it. Considering I paid full retail of $4,688 with shipping and taxes, I would have expected better.

6. This is a theoretical concern at this point, but I am worried that the chimney in my application will not be tall enough to provide sufficient draft. The manual blithely mentions solving draft problems by adding additional chimney sections, but I can’t realistically have 10 feet of chimney sticking up above the top of my truck. I don’t consider this to be a flaw in the toilet itself so much as an issue with my application. It would be nice, however, if the various marketing literature, or at least the owners or installation manual gave some guidelines for the minimum chimney height. They do at least mention the need to provide a path for inlet combustion air though they are very vague about how exactly that would be done. Fortunately, I already have plans in that regard.

The toilet came in a large cardboard box sitting on a wooden pallet. It was reasonably packaged with a mile of wadded up craft paper for padding, but not bolted to the crate in any way. Inside the box was the toilet itself, and a bunch of smaller boxes containing various chimney pipes, fire stop, pipe clamps, storm collar, chimney cap, etc. For some reason they shipped separately my catalytic converter (option), stainless steel toilet bowl (upgrade) and fire stop, which arrived several days later. There was nothing but some craft paper between the toilet and those other boxes to prevent marring the toilets nice shiny finish though.

My first impression is that the toilet looks nice. It has a clean external design, for the most part, and seems reasonably well made. I would not be embarrassed to have it in my home or cabin. If I had a cabin, or fixed point application, I would say that it is potentially a really nice solution short of putting in a septic system, or using a fair amount of electricity to do the same thing as the Incinolet.

The outer shell is made of about 1/8” thick PVC plastic, and is well formed, and polished to a nice shine. It has various louvers and access features mounted with pop rivets, and that is the first clue that we are dealing with something that is more or less hand made in low volume with whatever level of workmanship the worker bees were feeling up to.

The heart of the unit is the fire box. It’s a heavy steel box, surrounded by a bunch of mineral wool, surrounded by another heavy steel box. There are 4 primary openings into the fire box. The burner, or flame from the burner is blown down a heavy steel pipe from above, where is presumably spreads out on the floor of the interior and consumes the waste. Getting the fire to blow down requires a small squirrel cage blower. The entire blower/burner unit appears to be a standard unit taken from other applications, probably a furnace.

Blowing flame into the box poses a technical challenge though. The auger input that pulls waste into the fire box is not sealed. We can’t have super hot air coming out of the pressurized fire box back into the toilet bowl. As a matter of fact, it is clear that the designers intended air to be drawn into the fire box via the toilet bowl/auger opening. I assume this is accomplished in the same way as any fireplace must draw to prevent smoke from entering the room, using chimney effect.

That implies that the chimney needs to be very free flowing as it has to draw out more air than the blower/burner pushes in. This would seem to explain why they provide insulated chimney pipe that is 6” I.D. and 8” O.D. It also explains why there is a 10 ohm 20W power resistor in series with the blower motor to throttle it down. They need just enough blow to keep the flame from backing up, but not so much as to overcome the chimney draw.

The chimney related hardware is all very high quality from Duratech. It is not your standard hardware store double walled stove pipe. It is very thick walled, fully insulated, and has a polished chrome like exterior. The various other mounting hardware, flashing, roof supports, fire stop, etc. are also first rate, and come with an extensive manual describing various mounting techniques. This manual is just for the chimney related items, and has nothing to do with the toilet itself. Unfortunately, much of this stuff is of no use to me. If I were installing the toilet in a cabin it would probably be perfect though. I will use at least some of the shiny insulated chimney pipe, but much of the rest I don’t need.

The outlet from the fire box is a heavy steel 4” pipe which sticks out of the top of the toilet, and is mated to the chimney pipe. This connection is made to be fairly easy to remove via a double pipe clamp type coupler. The whole thing is then packed with mineral wool and surrounded with a latching section of outer pipe to make it look nice. The 4" pipe clamp coupler, while high quality, is the wrong size for the job. It runs out of adjustment just as it begins to cinch up on the 4" exhaust pipe.

The Auger inlet to the fire box is made from heavy cast iron with a steel auger. It’s very similar to a big hand crank meat grinder like you might use to make sausage, except that there is no grinding involved, just transport. The auger is driven by a modestly large worm drive gear motor. For reasons I don’t fully understand, the auger motor requires the 2nd 12V battery.

The one remaining input to the fire box is a heavy steel pipe for access to clean out the ash with a vacuum cleaner. It has internal threads and uses a heavy steel pipe plug with matching external threads. This pipe plug is buried under about 2” of mineral wool behind a sliding metal door that is part of the outer fire box.

This is where some of the limitations of the design really begin to show. You need to clean out the fire box when you use about 5 gallons of propane, which might be a month or two depending on how often you use it. That implies opening the rear hinged door, opening the outer fire box sliding door, digging out a bunch of mineral wool, unscrewing the pipe cap, sucking out the ash, and then putting it all back together again. I had envisioned something simple, like pulling an ash tray from the front, no such luck.

Since the access to the cleanout is in the back of the toilet you really need room to get back there. That implies that you can’t put the toilet any where near the back wall like you would for a conventional toilet. In my case I am going to make an access panel so I can get to this cleanout from the outside of the truck. Fortunately for me, that wall is behind the awning/door and not subject to weather.

Speaking of the back of the toilet, there is a big grey plastic box about 8.5” x 8.5” by 4.5” that houses all of the electronics and control systems. It is also in the way, preventing the toilet from being pushed up against a back wall. Reasonable access to that box would require at least a foot of clearance which is something I can’t afford. I have designed my exterior access panel to give me access to this box as well, and by giving up all my insulation space in that area I was able to get the toilet to within 1 ¼” of the wall in the back. The toilet itself is 34” long and 23.5” wide, so it takes up quite a bit of space as it is.

To be fair, the designers may have had a different idea about rear access. This toilet isn’t intended to be bolted to the floor. It’s supposed to just sit there. You can disconnect it from the chimney, and possibly the gas line, and then move it wherever you need to for access. I personally don’t think much of the idea, but being bolted to the floor is not a requirement in a fixed point application, and the chimney is designed to be fairly easily disconnected.

I am very concerned about maintaining a proper draft given the need for a relatively short chimney. I am also using a catalytic converter to keep the smoke and smell to a minimum, but It will also reduce the draft. I had already planned to bring combustion air into the toilet up through the floor. I now intend to bring that air in with a small 12V muffin fan to lightly pressurize the inside of the toilet and help push the draft along. That implies sealing all the possible air leaks. The toilet is nominally designed to draw combustion air from the room, so it has louvers on the back as well as air inlets on the lower sides. Air can also enter via the toilet seat or lid, even when they are closed. The entire top of the toilet comes off with an overlapping horizontal seam that is not meant to be air tight. Finally, there are a few small openings for the electrical wires or gas line.

I will need to seal all of these openings. The various louvers I can just tape over from the inside. Likewise the openings for the gas line and electrical are easily sealed. The horizontal seam is fairly tight to begin with, but a 1/4" strip of low density foam weather-strip seals it nicely. Some 1/4" white neoprene weather-strip did a neat job between the toilet lid and the seat.

The hard part is the seal between the toilet base and the seat. The gap is about 5/8” and somewhat irregular. My solution was to make a gasket out of two layers of 1/2” thick low density foam weather-strip that is attached to the bottom of the toilet seat. I then put a layer of silicon caulk on all the exposed surfaces of the weather-strip. With a layer of saran wrap to protect the toilet base and act as a release agent, I closed the toilet seat and lid and put a small weight on top to hold the seal fully compressed while the silicone cured. The end result is a custom fitted gasket that seals pretty darned well. It’s not the neatest job I ever did, but it’s not terrible either.

The air inlet muffin fan is mounted inside the floor of the toilet just ahead of the auger bracket. It taps into the same 12V line that runs the squirrel cage flame blower. That way it will only be on when the flame is on, which is only when the safety interlock detects that the toilet lid is closed. There is a corresponding opening in the floor of the truck box with a removable louvered cover and dust filter.

I thought long and hard about how to run the chimney up through the roof. Normally you would run the insulated chimney pipe right up through the ceiling and roof with various metal flashing to make sure nothing hot gets any where near anything that can burn, and then additional flashing on top to shed rain and snow. The typical home installation would be rather large and obvious, but in that setting no one would care. In my case I don’t want to advertise that I am burning anything inside, let alone crap, which would probably gross people out and get me kicked out of most anywhere. I need something a bit more stealthy.

Since the roof of the truck is already aluminum and therefore not flammable, I decided to stop the insulated outer section of the chimney at the underside of the roof. A heavy clamp bracket gabs onto the outer section of the chimney pipe and ties it into one of the wood rafters for support. I then built a wooden box around the pipe with clearance for fire proof insulation like mineral wool or fiberglass. The ceiling opening will then be covered with a tight fitting aluminum plate which will be painted to match the ceiling. Nothing inside should ever get too hot as it is all separated by insulation and multiple layers of metal.

Above the roof line, the 6” diameter inner pipe extends straight up about 4” and just stops. I didn’t want to use the conventional (and nicely made) chimney cap that came with the unit because it looks like a chimney cap. I also question whether it would prevent horizontal rain from coming into the inner pipe in a 65 mph rain storm. Instead I made my own chimney cap from a small oval roasting pan with stainless steel brackets that hold it 2” above the roof. The whole thing sticks up about 6” above the roof, and while it is plainly visible, it is hopefully not overly obvious.

I am still struggling with how to create a good rain seal where the pipe sticks up through the flat roof. If not for the heat I would just build up a heavy bead of roof sealant, but this pipe will get hot. The plan is to use a heavy bead of silicone, reinforced with some embedded fiberglass cloth, then a roughly conical metal ring flashing on top of that, with another silicone/fiberglass seal where the flashing meets the pipe, and where it meets the roof. All of this will be mostly under the chimney cap and will hopefully never even get wet unless the wind is really howling (like at 65 mph down the freeway).

The gas line will be heavy steel galvanized pipe under the floor of the box. It will poke up through the floor behind the toilet and the final connection will be made with a short length of thin wall stainless steel accordion pipe, of the sort that is made for gas lines. I am still worried about it cracking over time with vibration, but I can think of no better solution. I will also be making brackets inside the toilet to better support the gas line and everything attached to it.

I made a 1” thick plywood support that fits under the toilet to take most of the weight off of the plastic legs. It also gives me a solid location to bolt through the auger bracket and toilet housing all the way down into the wooden floor of the truck box. A little silicone caulk between the fire box and the spacers that hold it up off the plastic housing should help to keep it from moving around as well. Heaven help me if the truck ever ends up upside down, but it should stay put for most normal situations.

That just leaves the 12V and 24V electrical which I haven’t entirely worked out, but compared to everything else it should be pretty easy.

To be Continued…