How To Build A Composting Toilet

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Something perhaps inherent when venturing into unknown domain is the prospect of misallocating ones funds, by which I mean to say, spending too much money and/or spending it in the wrong places.

Here is a chief example concerning our tiny-house-on-wheels: the composting toilet.

I am going to talk about what a composting toilet IS, what it DOES, and how I built a fairly nice-looking one for less than $200.00 (Canadian), replacing our old store-bought model which cost us $1,250.00 last year! (Fortunately I was able to sell the old model on Kijiji which reclaimed more than twice the amount that it cost me to build the new one).

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Here is the only decent picture I can find of our old EcoJohn model ($1,250)

Back when we were building our 8’x20′ tiny house (started in July 2014), we were overwhelmed by the amount of projects requiring all of our attention. Not only were the projects vast in quantity, but they were also unusual by nature, meaning that we had no basis for knowing, for example, how a composting toilet worked. The esoteric quality that many of these projects possessed also made it more difficult to search out useful information – often we would have to sift through various unknown websites with contradictory opinions on the “best” way to get something done, only to leave us feeling uncertain as ever as to how we would proceed.

Fast-forward to our $1,250 purchase of the EcoJohn Basic-120 composting toilet. This model was priced very comparably to other models made by other companies, but it is my assumption that a large portion of the high cost was based on two aspects: (1) the model had a white plastic exterior made to resemble what we are used to seeing when we think of toilets, and this plastic shell was probably expensive for the company to have die cast; and (2) since there is a low demand for the composting toilet product in general (say, compared to regular toilets, for example), the lower runs of quantity would increase each unit cost when being manufactured.

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Here you can see the 5-gallon bucket inlaid with the biodegradable waste bag; the black plastic urine diverter (which connects to ordinary 1.5″ ABS drain pipe), and a 12V computer fan (glowing “LED blue” and attached to a 3″ dryer vent tube, which later connects to a 3″ PVC pipe that vents the odour outside.

So I want to get away from the costs of manufacturing a specialty item, and away from the costs of making it appear to look like a white, porcelain, toilet, the kind that we are all familiar with seeing. What remains? What do I need, as essentials,to make a functional composting toilet?

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Lots of storage in our bathroom, including inside the kitchen-adjoining wall, and inside of the home-made pocket door. 

Here I will compare the EcoJohn Basic-120 model, with the composting toilet that I made by myself for 1/6th of the price:

BASIC-120:
– waterless
– 120VAC (plugs into a regular plug outlet, using 0.66 amps (per hour)
– most of the electricity is used to operate a heating plate which is situated underneath the “bucket” where the waste is collected. I found this heating plate unnecessary: it is there in theory to accelerate the composting process, however, when we are changing out the waste bags on a monthly basis, the composting process is going to be very incomplete, with or without the added heat from the heat plate. Humanure (the process of properly composting human waste, as manure) is a long process that should be understood and followed carefully if one is ever going to use that manure for growing food or food-bearing trees. This can take TWO YEARS! So heating the waste for one month is not going to accomplish anything really, besides wasting electricity to run the heat plate. If you live off-grid, then all electricity is precious, and any effort to reduce your electrical consumption will save your battery power for more important efforts.
– the rest of the electricity is used to power a small fan which vents the odour outside.
– there is a built-in urine diverter, which sends the urine to the grey water drainage, because only excrement, and not urine, can be composted (this is true in general, and not just a comment on the Basic-120)
– urine diverter funnels into a 1/2″ exit, which means that urine must flow through a 1/2″ diameter tube, the small size of which I found to be insufficient

HOME-MADE TOILET:
– waterless
– 12VDC – the ONLY electricity that my model uses is to power a 12 volt computer fan, which I gerrymandered to a 3″ dryer vent hose, which connects to a 3″ PVC pipe and sends the odour outside. This fan runs on about 0.2 amps, and because it is 12 volt current, I do not need to use power from our INVERTER (a device which inverts DC power from our batteries into AC power for powering our plug outlets, a process which itself uses a little bit of electricity. So I have cut our toilet’s electrical consumption by about half an amp per hour compared to the old toilet.
– I built a wooden frame out of 2×2’s and then covered it in cedar tongue and groove boards, however, since the appearance of the toilet is not functional and only cosmetic, you can make it look however you want. If I had have not cared what the toilet looked like, I could have used plywood instead of nicer cedar wood, and I could have built the toilet for about $100 instead of $200.
– we needed a urine diverter, as urine is not compostable, so I bought an actual urine diverter online for $65, and this is the bulk of the real cost. If you can figure out a way to make your own urine diverter, you could build your own toilet for almost nothing. Again, most of the cost for me went into ordering the urine diverter part, and for using cedar tongue and groove boards for appearance. The rest is literally just a computer fan, a 5-gallon bucket, and some vent pipe.
– the urine diverter I ordered fits into a 1.5″ diameter ABS pipe, a standard size for indoor drainage, and much wider to allow instant drainage (versus the 0.5″ diameter opening on the Basic-120, which as I said before, was too small, causing an undesirably slow drain.

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Our bathroom is 4’x8′, lots of space if used properly. Here you can see to the left of the toilet, a 1.5″ drain pipe and two 0.5″ PEX water lines. We ran all plumbing on the inside of our interior walls, to prevent them from freezing in the winter. We then painted them the same colour of the wall, and hid them from view wherever possible, to assist in overall visual appearance. 

When we ordered the EcoJohn Basic-120, the company did not make its own biodegradable waste bags, but they directed us toward a site called DOGIPOT that sells them, and we still use these same bags in our new toilet. Humorously, the bags are made and targeted toward dog owners and dog parks, however, they accomplish the same task whether for human waste or canine. We bought a box of 50 for about $50, and we use about one bag per month.

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Biodegradable Waste Bags, about $1 each, and we use about one per month

This is probably enough info at this point. Write me if you have any questions. I would also consider building YOUR composting toilet, if you live in Ontario, and feel that you might want some help. 

Nature calls!

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