Compost toilet, bio toilet, dry (separation) toilet – many names for one and the same: a toilet. And it can fit anywhere: in your RV, in your self-sufficient (small) garden, or just behind the house. A composting toilet is a pretty useful thing – for you and your plants. And: It makes you a bit more independent. Here we show you how you can easily build your own composting toilet, what it’s actually good for, and what you need to keep in mind during (and after) construction. So go ahead: Discover the handyman in you!
No connection, no water: What is a composting toilet?
12,400 liters – that’s how much clean drinking water we waste every year just to flush the toilet. A hefty number, isn’t it? A bio or composting toilet, on the other hand, is a hygienic, water-saving alternative to the conventional toilet – without the need for a water or sewer connection.
With the composting toilet, feces are fed directly into a container filled with either bark mulch or straw, where they are composted. The excrement is subsequently used as fertilizer. It’s a pretty sophisticated system – but one that is phenomenally simple to implement. So building your own composting toilet is really easy.
Composting toilet and outhouse: what’s the difference?
Have you ever been to an outhouse? Then you know: It smells really bad there. And that’s exactly the difference to the composting toilet: In the outhouse, urine and excrement are mixed. This leads to fermentation processes and ammonia is released. In the composting toilet, the two substances are separated. This means that no unpleasant odor is produced in the first place.
How does a composting toilet work?
In the meantime, there are also different variants of the composting toilet. Depending on the manufacturer or need, the application, use and handling vary. In original composting toilets, for example, urine and feces are not separated from each other. However, this would be important for further use as fertilizer. We will now show you which different types of construction there are – so that you can build exactly the composting toilet you need:
Composting toilet with collection tank
A collection tank with a volume of 20 to 200 liters is located under the toilet seat.
The excrements (liquid and solid) are collected together in this container.
Emptying: into a garden composter or a central collection point.
Composting toilet with composter
A special composter is located under the toilet seat in a toilet room.
The urine is drained separately here.
The solid components are decomposed in the composter.
The compost can be removed through a removal flap.
Composting toilet with combination tank
Urine and excrements are stored separately.
The large collection tank is built into the floor.
It is large enough for approx. 2000 toilet visits.
Dry separation toilet
A mechanical separator is built into the seat of the toilet.
Most toilets have a built-in urine tank or hose to drain urine and a container for solids.
Urine and feces are consistently separated. The liquid urine ends up in the front area, and the solids in the back area, where toilet paper is also allowed.
The urine can be used to fertilize the plants.
For the solids, you can create your own fecal compost. For this, you should use your own litter to cover it after each toilet use.
How to use a composting toilet?
So there are many different variations of the composting toilet, but all models have one thing in common: they don’t need a sewer connection and (almost) no water. Flushing? Doesn’t exist. That’s what the tanks, bins, etc. are for, into which your solids and liquids are fed. From the outside, however, the composting toilet doesn’t look much different than its water-connected colleague: toilet seat, toilet lid – everything is there.
This is how you use the composting toilet: After you have done your business, you do not press the flush button here, but instead spread a layer of litter in the bucket. You can also rinse the urine separator with a splash of water.
What’s also involved is properly emptying the receptacles. Most segregation toilets have a urine hose installed through which the urine is directed into a separate tank. The solids also end up in a container. At 30 liters capacity, this is enough for 2 people for about 1 month.
The urine can be used as fertilizer and the solids as compost. So if you want to build a composting toilet, make sure you use the right composting method. You can read detailed instructions in Theresa Mai’s book “How we could live”.
Caution: Only use urine for your plants that is firstly diluted with water and secondly does not contain any drug residues (e.g. birth control pills, painkillers, etc.). The same applies to feces: here, too, be sure to find out in advance exactly how to compost the solids in the best possible way.
Building a composting toilet – what you need
Now you’ve gathered enough info and want to finally get started? Okay, but first: the preparation. Here’s what you need to build your own composting toilet.
Toilet lid, bucket, wood: materials
For your homemade composting toilet, you’ll need the following materials:
- Separation insert for the separation toilet, also called urine separator (you can get it at a hardware store or online), which you mount under the toilet seat/cover
- Canister to collect the urine
- Bucket for the solids
- Container for the litter
- Cover for the litter container
For the frame:
- several squared timbers (in thickness 40 x 80 mm)
- Roof battens or remnants of them, if you have some left over from remodeling/renovation (in the thickness 24 x 48 mm)
- wooden planks
- OSB boards
- four hinges
- door knob/handles
- many screws
- Now it’s time to screw: Tools
Of course, you’ll also need the right tools to build your composting toilet:
- Folding rule
- carpenter’s square and pencil
- Cordless drill
- Rubber mallet
- Angle plate
Build composting toilet: Instructions in 7 steps
If you want to build a composting toilet yourself, first think about where you want to put it. Do you have a small garden shed where it can fit? Or do you want it to stand on its own? If the latter is the case, then you should definitely include walls and a door. Here’s how to build a composting toilet for you now:
- plan, tinker, measure
If you already have a room for your composting toilet, start by measuring the space thoroughly. Keep in mind that the bucket and canister must fit under the seat and you should be able to sit comfortably. You’ll also need to allow space for your bedding storage if you want to include that as well.
- get the materials in shape
Saw the squared timber, OSB boards and wooden planks according to your measurements. The squared timber will form the frame of your separation toilet, the OSB boards and wooden planks will form the covers or walls.
- build the frame
Now screw the frame together and fix it to the wall or floor. Note that you still need to install a door on the front so that you can take out the box and bucket.
- the lining of your composting toilet
So that you don’t see the “bottom life”, cover the frame of your separation toilet with the cut OSB panels. And then fix another board or even wooden planks on top.
- adjust inserts
Now only the seat is missing. Measure where the toilet seat and lid will go and saw out a hole in the appropriate shape. In addition, if you have planned it that way, you can cut out the opening for your litter storage next to it and attach a small lid there later, too.
Tip: Of course, you do not have to install the litter storage, but it is more space-saving than having an additional container next to your toilet.
First mount the separating insert, then the toilet seat and cover with the cordless screwdriver. And do not forget the cover for the litter storage, here you can also attach a small flap.
- bucket and canister still pure and: ready!
Now place the bucket under the hole and attach a hose to the urine separator, which leads directly to the canister. Fill up your litter storage, e.g. with bark mulch. 7.
- and finally: insert the doors
Now mount the door with the help of the hinges. You can also add a lid with a handle for the litter storage. And voilà: You’ve done a super job building a composting toilet!
And now off to the loo? As you can see, it’s not that hard to build a composting toilet with our instructions.
Where to put all the manure?
Before you can use the compost from your toilet in the garden, it still needs time to decompose. To be more precise, it should mature for about 1.5 years. For this purpose, build a simple 3-box system with 1-2 m3 filling capacity each:
Box 1: for filling (this is where the contents of your collection container go).
Box 2: for maturing (the compost matures here)
Box 3: for storage (here is the filling material: leaves, chopped branches, straw etc.)
Your bin is full? Then fill it right away into your homemade compost bin:
Put on gloves, empty the container into Box 1 (filling box) and clean it with water (which also goes into the box) and if necessary with bio-disinfection, e.g.: Vinegar essence or essential oils.
Work the material in Box 1 into the existing material with a dedicated tool so that it is well mixed, and sprinkle a layer of filler on top.
When Box 1 is full, transfer the contents to Box 2 and mix everything vigorously.
At the end of the maturing period, do the fist test: Take a handful of compost and squeeze it (don’t worry, the material now has nothing to do with what it used to be). If it crumbles, you need to mix in some more water. If it’s too wet, add more bedding. If it’s wet like a squeezed sponge, the consistency is just right. Now you’re looking at dark black, fertile soil!
Compost toilet in the garden: What you have to consider!
In any case, keep in mind with your homemade composting toilet: absolutely pee sitting down! Otherwise the urine separation system will not work. You can empty canisters and buckets as needed, but in summer you should do this more often so that no unpleasant odor develops.
And where to put the substances? You can put the solids into the composter, the urine should be mixed with rainwater, then it is not too concentrated.
Toilet on tour: composting toilet for the motorhome
You like to travel and are always on the road with your motorhome, camper or van? Composting toilets are also ideal for this purpose, as they do not need to be flushed and therefore do not require water.
Everything you need for it:
- a self-made frame made of squared timber with covers
- a separating insert, a hose and/or drain with an odor trap
- a canister for the urine (12 or 20 liters) and a bucket for the solids (8 liters).
Here’s what to consider:
- You can build your composting toilet following the step-by-step instructions from above.
- Line the solids bucket with compostable (sanitary) bags.
- You can easily dispose of urine and solids on the go, e.g. at gas stations, campsites or municipal collection points.
However, make sure that the canister and bucket are properly secured so that they do not slip during the ride.
Law and order: Legal situation around the composting toilet
To make sure that the construction of your composting toilet is not a disaster, here are a few more legal facts for you:
- You don’t need a building permit for your composting toilet.
- If you process your liquid and solid materials on site in (i.e., your garden), there should be no health or safety concerns. Just be sure to use/compost/fertilize properly.
- Fecal matter should not be discharged into any body of water or onto common areas.
- However, there is no enshrined legislation regarding composting toilets as of yet.
- If you are unsure whether there are any regulations in your city or municipality, it is best to ask the relevant authorities.
How much does a composting toilet cost?
First, consider what exactly you need or want: a small toilet that you use once in a while, or a full-sized toilet that you use often? There are now many different manufacturers and models among composting or separation toilets.
The cost of these varies greatly:
For example, a small composting toilet without urine separation costs around 200 euros. Larger models with ventilation and full equipment cost around 1,000 euros. Even with the camping variants, you have to reckon with costs of around 700-1,000 euros.
Is it worth buying the composting toilet ready?
It is worth buying a composting toilet if you want a well-equipped composting toilet model. If you are not a passionate craftsman, then buying is the better option. Online you have a large selection and will certainly find the right toilet for your needs.
However, if you want to customize the toilet to your space and control your spending yourself, building is the better option. Depending on how much you want to spend, you can either use higher quality materials or save here and there. For example, do you have wood scraps at home? Perfect, you can use them right away.
Build composting toilet yourself – a toilet-rich idea!
Composting toilets are a low-odor, economical and ecological alternative to conventional toilets. They don’t need to be connected to a sewer system and you don’t need water for them – so you save money and energy. Want more reasons to build a composting toilet? It’s also great for traveling in a camper or van, or maybe even for your self-sufficient Tiny House. And by the way, you have super natural fertilizer for your garden. Ingenious, isn’t it?