Monday, December 16, 2013

Composting toilets edited

Edited to add missing pictures, scroll down to the bottom as Blogger is being fussy about editing today

Why would anyone want a composting toilet? It could be that you suddenly realized what is required to get a regular toilet to work. If you live in the city, giant electric pumps suck water from a local river, pump it to a water treatment plant, where trained technicians add various toxic chemicals and run giant filters, until the water is deemed clean enough to drink. Then more giant pumps move that water through miles of pipes to your house. Once at your house, you then take that precious drinking water, and....poop in it. Then it’s flushed down a parallel set of pipes miles back to a sewage treatment plant (helped along by yet more giant electric pumps) where it is cleaned up enough to flush back into a river, to carry your nutrients out to sea, where it contributes to excessive algae blooms.  Don’t care about the environment and being dependent on utility workers doing everything right? Maybe you know a survivalist, (true survivalists won’t admit to being one on the web, due to excessive government surveillance) and are contemplating living in a bunker with a year’s worth of food. That food has to go someplace, right? Or in my case, I am planning to build a sailboat. In the old days, you just sailed out to sea, and pumped the raw sewage out into the water. Nowadays, unless you are 5 miles out, you need a holding tank and ongoing pump outs, which are getting more expensive all the time. Holding tanks often have objectionable smells, and the plumbing bits always wait for the worst possible times to plug up, leak or otherwise fail.
I did some on-line research, and in boat sized units, there are a few choices. The fancy ones are AirHead and Natures Head, which appear to be a copy of one another, then there is the much more reasonably priced C-Head, The maker of C-head makes some very good points about basing his head on 5 gallon pails and one gallon containers, cheap, reusable and if necessary, disposable. Finally, I came across a DIY post on a tiny house blog for something in my preferred price range.  So I combined the tiny house blog design with the C-Head’s use of 5 gallon pails and one gallon jugs, to make my own design. One of the features that all the commercial units have is separation of poop and urine, for a number of reasons. First, separating the two means that much less duff, or absorbent material such as shavings, needs to be used to control the odour from the poop, and your pail will not fill up nearly as quickly. The pail, when full, will be much lighter to carry without the liquid, and the solids are not nearly as nasty to deal with as a slurry of both. If you have no place to compost the resultant solids, add bleach, then the container can be sealed with a lid (punch a vent hole) and disposed of in municipal waste, as legally it is the same as adult or baby diapers. The separated urine can be poured out in a toilet, or diluted at least 2-1 with water and used to fertilize your favorite plants (urine by itself is sterile). I went with Home Depot pails, as I discovered that there are variations in the pails (some manufacturers are making what appears to be 4.7 gallon pails so the unwary will not notice the smaller packaging) You can use any size that you have a good supply of or access to, but Home Depot is across North America. For the one gallon jug, I am using old windshield washer jugs, because I have lots of them.

Initial cuts

One pail will be sacrificed, to become the permanent portion of the toilet, along with half a sheet of ¾ inch plywood I had around. The other will be left as is, to be the collection chamber. Remove the handle of the sacrificial pail, and then cut the top of the pail off about an inch below the bottom reinforcing ring. The remainder is cut in half, and one half of that is used to make the urine diverter. I used a hand saw, utility knife and a heat gun to soften the plastic for the bends. The bends are not critical; I just thought that it made it easier to mount. Next cut a half oval out of the side of the upper ring, such that bottom part will lay in it sideways, with a slight downwards angle. Do not go below the bottom reinforcement ring, as this part will mate up with the other bucket. (Added the lost photos )I lost the photos of that stage of construction, so I will insert photos of the two cut parts installed in the lid.

urine diverter measurement

Once the plastic is cut, measure up for the box you will make up from the plywood. I took the idea from the C-Head to make the box a secondary containment, in case accidents happen. I think that the ¾ plywood is probably overkill, and a thin plywood box with 2x2 reinforcements would be enough, but with the heavier plywood, there is no fear if a much larger person was to use the toilet. When cutting the hole for the plastic parts, I originally intended that the lip of the upper pail would be proud of the plywood. However, I cut the hole to the same size, so it became a flush fit

There are four wood screws that catch the lip, then a generous amount of glue was used around the lip on the inside and out to seal everything in place. My box has feet cut into the corners at the bottom, and a 2 inch plywood lip under the top piece, with the top extended on either side to make it easy to lift up (no wasted wood, that was the width of the last piece I cut, and I could have just as easily made one more cut to make it as small as possible). All wood will be painted with an exterior grade latex paint, and the corners rounded with a router or sanded to taste. My design is hinged at the front, so it can be put back against a wall. There are 2x2 inch 45 degree cut pieces at the back, so that everything automatically aligns once closed.
Front view

Completed lid open

Distance to bottom of collector pail

Detail of seat attachments

foot detail

A drain hole is cut in the bottom of the plastic urine diverter, to fit whatever hose or adapter you have or get. I used a hot melt glue gun to secure it in place, and make sure that there were no low spots that would not drain into the hose. I cut a door into the front of the box so that when closing the lid, you can make sure that the hose actually did go into the one gallon jug. My design has room to have a spare jug inside it for when the first gets full and it’s the middle of the night.
Additional notes: get the longer, oval seat. I tried the cheap round seat but the room for an adult to properly aim is badly restricted, so took it back and paid the premium for the better seat. The seat I got has quick removal for cleaning attachments, not required but makes fitting things up easier during construction. I added some scrap pieces of plastic pail at the back to seal things up. After painting, I plan to use foam rubber weather-strip around openings to control airflow as required. Also, this design will be too tall for most people to sit comfortably, so I am making a foot stool to bring my feet up to ideal height. My home toilet is called a “comfort height” and is 16.5 inches to the top of the ceramic portion. It is mid way between the shorter ones made for kids, and the taller handicap style toilets. I recommend that you measure the height of one you like, and then build your footrest for that height.
All the information I have read indicates that a vent fan, using a little fan from a computer, may be required. If so, I will cut a hole in the back and attach the necessary hose and fan. Most any dry type absorbent material can be used to cover up the solids, I plan on using pine shavings, sold at the local lumber place as animal bedding. Another 5 gallon pail will hold the fresh shavings and a scoop.  A squirt bottle filled with a water/vinegar mix or commercial deodorizer is kept on hand to spray the urine portion after use. For men, a companion urinal made from a gallon jug and automotive funnel screwed to the wall at the appropriate height will simplify things, and satisfy He-men who refuse to sit and pee.  
This spring I intend to remove the flush toilet from our 5th wheel and install this as a trial. If everything goes as expected, this is the toilet that will go in the sailboat I am building, and counts as the first component of that sailboat (gotta start somewhere, and there is two feet of snow outside, so it needed to be a small start)
Dennis Donohue


Top view complete

Plastic parts mostly cut

Diverter fit to top ring

Screw for holding lip of top pail


  1. and will it be tested ahead of time? At say, a wine tasting?:) And what about the worms??

  2. That is the fanciest Home Depot porta john I've seen. At least the most important part of your sailboat is now complete.

  3. That is an excellent way to save money on a DIY diversion toilet. I may just have to try this for my shuttle bus RV conversion. By doing a composting toilet, i'll save valuable space normally planned for a blackwater tank, instead to move diesel fuel into that tank and then use my regular tank for waste veggie oil for longer distance driving. Amazing what going to this type of setup would do for me.

  4. Amazing thanks sawdust can possibly be used ? thanks

  5. Best do it yourself compost toilet I have found so far!!!

  6. This is great! I love the homemade version of the urine diverter. In case it's handy for anybody who wants an intermediate version, here's what we set up for my boat, with the bucket system and a commercially available diverter (much cheaper than commercial composting heads). How has your system been working out for you in practice? Have you been happy with pine shavings? Thanks so much for posting all those great instructions and photos!

  7. Looks uncomfortable for the legs while sitting on it. I would think it better to shape the wood box to the seat instead of having square corners where someone might want to open their legs a little while seated.

  8. No problems with comfort in real world usage, and to build plywood curves, while possible, makes it a work of art, not a do it yourself box. Not to mention that if you are capable of building such a fancy wooden construction, the 5 gallon bucket would bother you. You could go for a simple Lugable Loo, but they do not separate solids and liquids, so everything is a compromise. Anyway, thanks for reading my blog


  9. Thanks for your sharing, I will learn about this product.
    find this

  10. We're liveaboards and have used a simple bucket composter for going on five years now. I'm definitely going to give a version of this a try (I may have to find a way to shorten your design a bit). The design looks entirely workable. I should be able to put the urine collector in the space currently occupied by our humanlitter container (you can see our setup over at Thanks for the great information.

    1. Okay, I think I figured it out. I'll have to reverse the urine collector so it's mostly over the opening of the bucket. That should work in the space we have. Let ya know how it works.

  11. Gracias, muy ingenioso el modelo!

  12. Nice job. There are many designs online, but this one is by far my favorite! I appreciate your work.

  13. Gracias, importante infirmacion.

  14. Tell me more about the way you connected the tube to the urine diverter. Have any detail pictures? I found a urine specimen collection device to use for $1.53 plus free shipping from Allegro Medical. Fits in the toilet well. Just need to add the tube. How is the hot glue holding up?