Imagine that you are in your garden plot and devote yourself to gardening. At the latest when you hear the call of nature, good advice is often expensive without a nearby home. Often decried as an absurd idea by eco-idealists, the composting toilet is able to solve your problem reliably and at the same time for the benefit of your garden. Build your own urine-diverting toilet with our assembly instructions.

composting toilet

Before you start building your own ecological toilet yourself, we will inform you briefly and concisely about what it is about in detail and what you can expect as a future user:

  • waterless toilet
  • Composting of the faeces in the sense of a closed nutrient cycle
  • Possible further use as fertilizer in your own garden

Build your own composting toilet

To implement a composting toilet, there are several options for dealing with the collected faeces. Our assembly instructions refer to the construction of a so-called Separating toilet. This has the following special features:

  • Separate collection of urine and feces
  • Further use of urine, for example, highly diluted as nitrogen fertilizer
  • Alternatively: Empty the container into the sewage system
  • Effective and low-odour aerobic composting of solid faeces in the composter
  • Bark mulch, straw or sawdust as an auxiliary material for sprinkling and for better composting
  • Composting of the manure either directly in the composter under the toilet, or at a separate location in the garden

We assume that the toilet is to be housed in an existing garden shed. Although it would be possible to implement the composting toilet without such an enclosure, we assume that privacy and weather protection also enjoy a certain value in the garden plot. You could certainly also build the garden shed yourself, but for this you have to refer to the corresponding separate building instructions.

The construction of a separate toilet building with composting taking place directly under the toilet would also be a real alternative. Here, too, we deliberately decided against it when setting our goal, since this arrangement means an enormous amount of additional work, which in many cases would lead to a KO of the toilet issue. Instead, we envisage a collection of the faeces in the toilet, while the final disposal has to take place elsewhere in the garden.

notice: In order to make our toilet as natural as possible, we use wood as the basic building material. Although other materials would also be possible, wood best reflects the ecological approach of the urine-diverting toilet.

The materials

The following list of materials is, in our opinion, well suited for building the composting toilet yourself. If you have different materials at home, you can also use them as long as they fulfill the intended function just as well. Therefore, before starting your work, please read these instructions carefully and, above all, through to the end.

wood

  • Three-layer panels d=19mm
    • 2 pieces 60x100cm (A)
    • 2 pieces 60x45cm (B)
    • 1 blank 96x45cm (C)
    • 2 pieces 47x44cm (D)
  • squared timber 44×44 mm
    • 4 blanks 45cm (X)
    • 3 pieces 88 cm (Y)

tip: It is true that you can laboriously create the required wood cuts yourself. However, a circular table saw is almost absolutely necessary for a dimensionally accurate result. It is therefore best to have the individual parts cut to size directly at the hardware store.

Others

  • Wood screws countersunk 4x40mm for connecting the panel cuts to the squared timber
  • Piano hinge b=32mm, 2 cuts each 44cm including suitable screws
  • 2 magnetic closers for furniture doors including suitable screws

notice: You could theoretically screw the plates together directly. However, since a screw screwed into the front edge of the panel has little pull-out resistance and the panels tear easily, we use squared timber for the corner connections. These function as a replacement for metal brackets and allow the panels to be connected in a force-fitting manner across corners.

  • PVC sewage pipe DN100, length according to local conditions, approx. 200cm
  • Matching elbow 90 degrees, 1 pc.
  • Alternatively: pipe elbow 45 degrees, 2 pcs.
  • Matching pipe clamps for wall mounting, approx. 3 pcs.
  • Cover grille DN100, 1 pc.
  • Canister as urine collection container, maximum height 40cm (!!)
  • Plastic box with closed walls, max. width 40 cm, max. height 40 cm, max. width 96 cm less canister width + 5 cm
  • bucket
  • Dustpan, ash shovel or cf.
  • Separating insert for composting toilets, e.g. Separett Privy 500 with thermal seat
  • Combination wood varnish primer and top coat in one

notice: It is true that the dividing insert that is absolutely necessary for the urine-diverting toilet could also be made by yourself. However, these solutions are not very convenient. That's why we use a finished product that can be used to easily separate urine from faeces during a bowel movement and that also has a comfortable seat. Anyone who has ever used an outdoor toilet at low temperatures appreciates the luxury of a seat made of foam plastic!

For later operation

  • bark mulch, straw, or sawdust
  • Compostable bin liners

required tool

  • Jigsaw with curve blade
  • Cordless screwdriver with bit set
  • Forstner bit approx. 20mm
  • Brush, cloth, possibly solvent
  • Sandpaper or wood file

Build a composting toilet yourself: instructions

After all the required materials and tools are ready, we start to build our composting toilet ourselves. It is best to implement it directly in the garden on site, since you then have short transport routes and can set up the system completely. But it is also possible to prepare the actual toilet box at home in the workshop and only then transport it to the garden where the final installation takes place.

We need the toilet box as the basis for setting up the separation toilet. The seat will be installed on it later. There is also space for collecting containers for urine and faeces.

Note: The 4x40mm countersunk screws are used for the connections described below. All connections are made using panels on squared timber. A screw should be placed at each end of each connection and the space in between should also be screwed at intervals of no more than 20 centimetres.

Step 1 - 5

1. The preparation:

  • Deburr all blanks along edges with sandpaper or file
  • Roughly sand surfaces to remove loose wood fibers

2. Creation of the side parts:

  • Place a squared timber section X parallel to each 45cm edge on side panel B, and indent 19mm from the outer edge X and screw (results in a vertical corner connection)
  • Repeat the process with the second side panel and the remaining sections X

3. Back

  • Erect the finished side parts on a 60cm edge, screwed-on wooden parts pointing inwards
  • Position rear side C between side parts B and screw to squared timber
  • Screw one blank Y flush on the inside along the 96 cm edges on the back C (between blanks X of the side panels)

4. Lid and base

  • Place cover A on blanks X and Y and screw together
  • Turn the box over and repeat the process with the second blank A as the base
  • Screw on the remaining blank Y on the inside of the cover 19mm behind the front edge
  • Turn the box over again so that the bottom part (without the blank y screwed on at the front edge) = standing area

notice: The squared timber blank screwed onto the front of the box is used on the lid for additional stabilization when sitting on it. It also serves as a stop for the following doors. On the other hand, on the bottom part it would be a hindrance for the faeces and urine containers and is therefore omitted.

5. Assembly of the doors

  • Provide door elements D with a bar hinge along a 44 cm edge for each element, screw the hinge into the panel on the front side
  • Drill a hole with a Forstner bit on the opposite 44 cm edge in the middle of the panel with a distance of approx. 4 cm from the edge, file or grind the edge of the hole
  • Screw the door elements to the side parts B using the hinge on the front side
  • Build the magnetic door closer on the door and screw the counterpart to the box lid

Step 6 - 7

6. Toilet opening

Now the toilet opening is created on the top of the toilet box. Unfortunately, no absolute dimensions can be given for this, since the opening primarily depends on the selected divider insert. This indicates the exact shape - usually round - and the size of the opening. The location, on the other hand, depends on the dimension of the selected containers for the faeces. Ideally, the separating insert is located in the middle above the manure box. Since this cannot be in the middle of the box next to the urine canister, the position of the seat with the separating insert will rarely be in the middle of the urine-diverting toilet.

  • Mark the opening for the dividing seat and saw out with a jigsaw
  • Grind or file the edges of the holes

tip: The opening of the composting toilet should be as far forward as possible for comfortable sitting. However, the sitting seat must not protrude beyond the edge of the box, otherwise the styrofoam will quickly deform and break at this point. In addition, the manure box can be used more efficiently the more centrally the opening is placed above it.

7. The coating

  • Coat the inside of the box completely with paint according to the manufacturer's instructions
  • Paint the inside of the door in the same way
  • The outside of the box can also be painted as an option

notice: The paint on the separation toilet is used for easy cleaning and better hygiene when dealing with the faeces. Since these are primarily in the box, the coating there is essential. The unaffected outsides do not necessarily have to be painted. However, it is advisable to apply paint at least on the upper side to ensure the necessary hygiene in the area of the seat. You can either apply the coating yourself in the classic way, or alternatively apply it as an adhesive film.

Step 8 - 10

8. The exhaust vent

Since composting depends on sufficient oxygen, the separation toilet itself must be equipped with an exhaust air system. This allows decomposition gases to escape. In addition, a chimney effect created via the exhaust air pipe ensures a minimum change of air, since air escapes upwards and can flow through the generous gaps in the door.

  • Using the exhaust pipe, mark the opening on the back of the cover, e.g. in the rear corner on the side
  • Saw out the opening with a jigsaw, grind or file the edges of the hole

The basic body of the urine-diverting toilet is now complete. It can now be positioned in the garden shed as you wish. The location on an outside wall makes it easier later to build the exhaust air duct on the wall.

9. Exhaust installation

  • Plug the DN100 line into the exhaust air opening of the toilet box
  • Run the cable up the wall
  • Attach the arch and mark the wall opening on the wall of the garden shed at the arch exit
  • Create an exhaust air hole in the shed wall with a jigsaw, deburr the edges of the hole with sandpaper or a file
  • Attach a short piece of pipe to the floor and guide it through the wall
  • Fix the exhaust air line to the wall with pipe clamps
  • Attach the cover grille to the exhaust air pipe outside the wall

10. The Completion

It's almost done to build your own composting toilet. Only the "setup" is still pending:

  • Place the divider on the toilet opening and fix according to the manufacturer's instructions (if necessary)
  • Place the canister sideways in the toilet box and insert the hose of the dividing seat into the canister opening
  • Put a garbage bag in the manure box and push it into the box next to the canister under the toilet opening
  • Place a bucket and shovel of mulch or straw next to the toilet seat

The operation

With these simple steps, the building is finished and your own, self-made composting toilet is ready for use. After each bowel movement, a handful of the sawdust or straw provided is simply placed on the droppings. This process replaces rinsing, so to speak. If the urine canister or droppings box is full, they are removed and emptied. The content can be handled as follows:

urine

  • Disposal in the sewer
  • Use as a nitrogen fertilizer in a highly diluted form, e.g. with collected rainwater

feces

  • Composting in your own garden in the composter or on the compost heap

notice: Although the actual composting of the faeces takes place in the composter, it is important to always scatter after the stool. On the one hand, the droppings are covered in this way. On the other hand, the decomposition bacteria can already develop here. With the carbon in the grit, you will find optimal conditions and create optimal conditions for later composting in the composting toilet.

Category:

Garden design