Why I have a funny-looking toilet, or How to Build a Tree Bog in Five Easy Steps

July 30, 2007

First off, if you haven’t already read it, I got the idea for this project from the Wikipedia page, here.

Our ‘bog’ isn’t quite the same as any I saw when doing my research, since most of those seemed to use a – ehem – more direct gravity feed system, i.e. a box directly over a hole, just like any traditional pit-toilet or outhouse system. The main difference/advantage of the tree bog is that the waste material is [supposed to be] recycled so effectively by the willow hedges that the structure will never have to be moved or re-dug. Also, the rapid transformation of the waste and the buffering effect of the hedges themselves should reduce odor to the extent that the structure can be near or built onto the main building, which avoids those charming mid-winter or rainstorm dashes to the more remote traditional outhouse.

Based on the pictures I saw, I would guess that most of the tree bogs I was looking at were either being built into (/onto) newly erected homes, or added to cottages where they were replacing an outhouse system. We have an old house with installed plumbing, and are replacing a flush plumbing system with the tree bog. Due to the size and layout of the house, it was impracticable to build the toilet out directly over the hole, so we are using a combination system derived mainly from the tree bog idea, but borrowing elements from commercial composting systems. Which is to say, we kind of made the whole thing up as we went along.

We started with the ground floor bathroom, for several reasons: One, it was already broken, making it a prime candidate for replacement; two, the toilet-to-composter distance was small and simple, so although the upstairs will have a sharper angled drop, facilitating gravity, we still think it will be easier to troubleshoot with the smaller and more accessible system.

The system itself is ridiculously easy. We dug a hole outside the house. The hole slopes away from the foundation to prevent future tree root damage (not a big concern for our house, since it hasn’t got deep foundations, but something to keep in mind and better safe than sorry, and all that. The deepest part of the hole is about 3.5 or 4 feet deep, 3 feet wide, and about 2 feet at the base leading to the slope. The depth depends on the volume of waste produced by the household in a year, Wikipedia recommends about .75m3 per person per year. (In determining volume we also factored in the second toilet, which will have its own box.)

Then we built a box over the hole to enclose it. Our box does have a lidded top, in case we need to get in there, the top will be padlocked for health and safety reasons. Vents are cut into the lower edge of this box for air circulation, then covered in hardware cloth (chicken wire works too) to keep out curious mammals of any description.

The hole is then loosely packed above vent level with straw and dried grass. This will soak up moisture and help to suppress odor while the composting process begins.

A hole is bored through the wall at whatever level and angle is appropriate to connect the toilet. This depends on what you’re using for a toilet and how the pipe is connected, details of ours are below. The pipe extends into the box and out far enough to get the waste down the slope and into the straw. The length of our pipe may be adjusted later, depending on how it all works!

Outside the box is the Tree part of the Tree bog – some willow shoots (more are being started elsewhere, we haven’t wanted to plant them all here until there are some nutrients to feed ‘em!). The intention is to surround the box with willow, which will feed on the waste, conceal the box (thus reducing the number of times you hear “hey, what is that box? It’s WHAT? EEEW!”) and reduce odor. Given yet another opportunity to landscape something, my husband has also planted mint, ivy and oleander, which should a)take over quick and make it pretty and b) counteract any escaping odor by Smelling Very Nice.


Inside, we’ve modified an old dining-room chair we found to be our new toilet. We removed the upholstered seat and replaced it with one made of 2/8” board. A hole was cut in the new seat to accomodate the bowl – a plastic mixing bowl.

The mixing bowl was selected largely (almost exclusively) because the base of it fit into this weird pipe thing we found. The weird pipe thing, which I’m sure based on where we found it in the hardware store has some perfectly sensible and practical use probably having to do with “normal” toilet plumbing systems, was the most expensive part of this project – about seven Canadian dollars. What it does is connect the horizontal base of the bowl to a 45º angled pipe. It is designed to be screwed down, so it is fixed to the seat of the chair. The bowl sits into it with a gasket, so that it seals but can be removed for cleaning.

In the spirit of odor-prevention and general emotional comfort, there will be a lid fitted to the bowl. A 1/4 cup of wood ash dropped into the system every now and then is also supposed to help with odor, just as it does with any pit-toilet. We heat with wood, so will have plenty of ash available to add to the system when needed.

And that’s the story so far! I will update this page as the system gets up and running, and add any problems or alterations (or hopefully successes) that we encounter. Meantime, feel free to post or email your comments or questions, and I’ll answer as best I can!

August 6, 2007

It’s working! Got the whole thing assembled in place, and Raven put a bead of caulking on the end of the pipe – while it cured we set the bowl in place with some saran wrap under it, so that it would dry in the right shape to act as a gasket. I don’t want leaks, but I do want to be able to remove the bowl and wash it if necessary – And I’m not interested in putting soaps or cleaners into the bog system.

It has now been tested thoroughly by me – I’ve been living with it for a few days – and also by two guys. Raven’s still in Windsor and hasn’t used it yet, but some old friends stopped by the other night and gave it a try. Don’t seem to have been any problems with splashback (sorry folks, but it’s a real issue!) and one of them is quite tall, so that was kind of an important question, actually!

Best thing so far – it needs hardly any water. I had brought a two-cup measure in, and haven’t used more than a cup – and usually less – so far. So, we won’t be adding tons of extra water to the system (good thing) and my golly – just compare that to even a low-flo toilet. One cup of water!

Now I get to focus on making it (and the room around it) pretty.

August 20

Well, nothing to report, really. It’s still working, there have been no clogs or anything – the best news so far is that even in the recent heat wave there’s been no odor to speak of, inside or out. So the vents must be working too! Don’t know how clear they’ll stay in winter – depends on how much heat the thing is able to generate, I guess. We’ve planted the willows all the way around the box now, but they won’t have taken well enough to do us any good keeping the snow off the vents this winter – maybe next year.

January 24, 2008

It’s been really cold this past week or so. Up until now it’s been a fairly mild winter, but the last week is more of a “what you can expect in Canada” sort of thing. So this has been the first real deep-cold test of the ol’ bog. And sure enough, at some point over the past week there must have been a clog – my guess is paper, wet paper being the most like to freeze and the least like to shoot smoothly down the chute, so to speak – which, going unnoticed, resulted in a big frozen clog in the pipe. Which we discovered yesterday morning.

This could have been prevented. What I should have been doing was tossing a cup of boiling water down the pipe every day to make sure it kept clear, and that *ehem*solidmatter*ehem* was not piling up and freezing under the outlet. But I didn’t. duh.

It was only the length of pipe outside the wall that was frozen, so rather than add heat inside, I boiled a kettle and poured it on the pipe outside, in the box. Raven says anyone building one of these please note: make sure you place your pipe so that it can be reached without climbing into the box! Which luckily, we did. I can’t actually touch the pipe, it’s too low – but I can pour water on it, which is what was important yesterday.

This worked fine. Took about five kettles – I poured water on the pipe, then banged on the pipe with a stick while more water heated. The clog began to loosen right away, and at last it came free, the pipe drained, I used my stick to clear out under the outlet, and we were back in business. This is probably about the worst thing that could possibly happen, it could have been very easily prevented, and fixing it was not a big deal AT ALL. Compared to what Raven had to deal with last year when the septic drain froze, it was a walk in the park!
(Almost literally – I was outside in the sunny yard, rather than bellycrawling under the house, and at no point did I have to come in physical contact with any waste material. Or even dirt.)

I also noticed that although the top layer of water in the pit was frozen, it was wet underneath and the semi-solid muck near the outlet was just that – muck. Which means even in these temperatures the bacteria is still actually working and generating some heat. Which in turn would explain why one of the plants nearest the box still had green leaves last week.

Still lovin’ the Bog.

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12 Responses to “Tree Bog”

  1. Dru Says:

    Sorry to ask a delicate question in a public forum… but “those who visit” (well mostly just me) are curious

    The bowl seems… umm… shallow ? How do I ask this… delicatly…

    is there room for pile up ? or does it slide nicely down the tube ?

    🙂

  2. Kelly Says:

    So far, um -things- have been sliding even more nicely down the tube than I’d expected. Because I was worried about that too, of course! The only thing we haven’t tested yet (due to my being a girl, and on my oddy-knocky right now) is whether there is comfortable room for a guy to sit, given that y’all apparently have some arcane “tucking” thing that needs doing. If we encounter a problem with this, then we’ll have to raise the seat a bit and install a deeper bowl, but I think width is more the issue there, and there should be plenty. I’ll keep you posted!

  3. Dru Says:

    Thanks. I was mostly just kidding around a bit. Mostly

  4. lee Says:

    this is extremely cool.

    I have the willows, but they are not around a bog – they are just taking over the back yard and trying to climb in the kitchen window.


  5. How is it going now? We are considering a compost toilet for indoors, one which would need emptying. And I was thinking of a treebog for outside, to be used when gardening and in good weather. In summer we are almost always outside.

    http://en.wikipedia.org/wiki/Tree_bog

    Regards, Rebecca in Ireland

  6. Leif Says:

    How cool is this? Great page, great to hear of an in-house tree-bog. Answered several questions. Will be checking for your updates in the summer…

  7. sally in Warwickshire, UK Says:

    Hi,
    Cool bog!
    We have the willows already, but in quite boggy ground. Is the high water table a problem?
    Also, we won’t be using directly, but emptying portapotty from our (liveaboard)narrowboat – is there any likely problem with putting in a potty’sworth every few days?? (We don’t use chemicals, just biomagic.)Thanks in anticipation, Sally.

  8. Heather Says:

    21 years ago my husband and I homesteaded on acreage in the US Pacific North West. It took some trial and error, but basically, necessity, plus intuition and ingenuity created our bog plans. Just when our modestly functional lifestyle might have really begun to pay dividends, if we had continued to adapt and grow with alternative, permaculture and sustainability guidelines, my husband went MANIC. We took a big loan to finish building our Timber Framed dream home, more conventially and grandiose than necessary, including 2 full baths, with a standard septic system and drainfield. Then, shortly thereafter, the economy took a downturn, along with his mood, making our morgage payments impossible, so we had to sell the property! These many years later we can only hope we still have the stamina to pull off another homesteading adventure in our fifties. Utilizing human manure may seem crazy, but decentralization and personal responsibility = freedom.

  9. Wanda Says:

    Wow! Thank you for this information. I believe we had the perfect spot for something really similar to your Tree Bog. I was just a little lost on the details for installing the bowl to the pipe to achieve no leaks while still keeping it removable. Is the bottom of the box just wire mesh over plain ground dirt? If you have additional pics detailing these steps, would you mind forwarding them to me? Thank you for making this information public.

  10. quavasela Says:

    Great story, I did not thought reading this would be so cool when I klicked at your title with link.

  11. Chaosgarten Says:

    Seems the willows can’t absorb all the nitrate so it contaminates the groundwater.
    http://chaosgarten.blogspot.com/2011/06/treebog-tree-bog-grundwasserverseuchung.html (german).

    1. Kelly Says:

      Not sure what you mean by this – nitrates are naturally occuring – VERY natural in the case of human waste – and would be going into the groundwater in any case in a septic system, which has got the same naturally occurring bacterium but has not got plants specifically placed to help reduce distribution. Granted I am not a scientist (at ALL) but this sounds like an artificial concern, possibly disseminated by someone with a financial interest. Example: no-till farming reduces emissions. It also involves dumping vast amounts of herbicide on the fields. Obviously this can be ‘spun’ two ways.
      In either case, high-nitrogen soil simply must be combatted by mixing and mulching – in the same vein, I mix both sheep and chicken manure as well as compost in my soil, chicken manure is abundant but too strong on its own. Human manure is actually excellent fertilizer (chemically speaking and used responsibly in a bacterium context, don’t mistake that as advocacy!) “Groundwater” in the case of a three-foot deep hole in clay soil absolutely does NOT affect drinking water, if that is your concern, and obviously anyone replicating this system would need to be aware of their own drinking water sources.

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