The ultimate guide to building a composting toilet yourself: How can I build a composting toilet myself and what do I need to look out for?

Replacing a cassette toilet with a dry composting toilet - is that possible?

Most motorhomes have a factory-fitted toilet. This is usually a cassette toilet. If you want a more environmentally friendly option or are looking for a way to be independent of disposal stations on the road, a composting toilet is an ideal solution.

Don't worry! You don't need a new vehicle. It’s entirely possible and straightforward to remove the chemical toilet and install a dry composting toilet, as shown, for example, in the report by Kay, who installed a Trelino® Origin L in his van.

Regardless of whether it's a bench toilet or a swivel bath, with a little manual skill a conventional camping toilet can be removed from any vehicle and replaced by its sustainable sister. Likewise, new conversions can be planned directly with a dry composting toilet.

What to do if no dry composting toilet can be found?

If none of the current models suits you, your vehicle, your garden shed or your Tiny House, you can of course also build a composting toilet yourself. You have the choice between complete DIY or the use of ready-made components such as a solo separation insert or a whole set that includes not only the insert but also the canister and the solids container.

Whichever you choose, there are no limits to your imagination and creativity when you build your own. In this way, you can fully adapt your quiet place to your individual needs and the space you have available.

In this paragraph, we explain the advantages and disadvantages of building your own composting toilet.

We have created a separate article on the advantages and disadvantages of buying and building your own composting toilet. You can find it here.

Build your own composting toilet: These are your advantages

Building a composting toilet yourself has several advantages. Your dry composting toilet needs neither cassette additives nor water. This means you can choose an environmentally friendly and sustainable toilet. Other big plus points are the ease of use and cleaning as well as the uncomplicated disposal of the waste.

The separation of solids and liquids and the drying of the solids also reduce the formation of odours, making it much more pleasant to use than other types of camping toilets. And if you want to use the composting toilet in your garden shed, you can use the collected urine to make high-quality fertiliser for nitrogen-tolerant plants.

If you build your own dry composting toilet, you can adapt it to your individual needs and circumstances. You can choose the design, size and materials that best suit your space or vehicle and your budget. In general, a self-built composting toilet is cheaper than a ready-made model.

Build your own dry composting toilet: These are your disadvantages

While building your own composting toilet has many advantages, there are also potential drawbacks to consider. Although there are many advantages to building a composting toilet, there are also some potential disadvantages that you should be aware of and weigh up.

One disadvantage of a self-built tremm toilet is that it may not meet the same quality standards of a finished model. Inadequate planning, lack of craftsmanship, the wrong tools or even the wrong material can mean that the dry composting toilet does not fit into the intended space in the end, the statics and thus the load-bearing capacity are not optimal, the seating is uncomfortable or the containers do not fit into the body or under the separating insert, making the composting toilet unusable.

Building a composting toilet can be time-consuming. Especially if there is a lack of experience or if the tools are not suitable for the project. If the self-construction takes much more time than expected or planned, this can be frustrating.

Another disadvantage of a homemade composting toilet is that it may not be as durable as a purchased version. If you use inferior materials or tools, there is a risk that the clog will wear out or be damaged more quickly than a high-quality dry composting toilet.

Last but not least: If you build a complete toilet house around your composting toilet, you should find out beforehand to what extent the construction must - and ultimately does - meet the specifications in building regulations.

Planning and preparation

Have you decided that a custom-built composting toilet suits your needs best? Then it's time for planning. Before you screw in the first screws or swing the hammer for the last time, it's time to go to the drawing board. Here are some criteria for you to consider when preparing to build a dry composting toilet:

The model: decide what kind of toilet you want to build: dry or dry composting toilet? There are different models, from simple bucket toilets to elaborate composting toilets. Consider your individual needs and budget.

Placement: Consider where the dry composting toilet should be placed and whether there is enough space. Also consider the humidity or ventilation of the room. These things play a role in the choice of material.

The material: Choose a material that best suits your toilet variant and that is robust enough to withstand the stresses and strains of the quiet lavatory. Bear in mind that wood can swell in damp places and tend to grow mould. It is good to use materials that are moisture-resistant or can be well impregnated.

The use and emptying intervals: Do you use the composting toilet alone or are there several people who visit the quiet little toilet? How often will the toilet be used, is it more of an emergency toilet or should the composting toilet be used every day in the Tiny House? How often can and do you want to empty the dry composting toilet? All these factors - together with the space you have available - determine the size of your urine canister or tank and that of the solids container.

The necessary tools and materials: Before you start building, you should make sure that you have all the necessary tools and materials to hand. From wood to screws and nails to hinges and the appropriate tools: cordless screwdriver, hammer, jigsaw... everything it takes to build the composting toilet of your dreams. Nothing costs more time and nerves than having to interrupt your work again and again to go to the DIY store because a part is missing or you got the wrong tool.

The installation: Think about how the toilet should be installed. Should it be fixed to the wall or stand on the floor? What kind of ventilation is needed to minimise odours? Make sure to carefully plan all the necessary steps to install the toilet correctly.

Careful planning and preparation will help you build a composting toilet that will be fully functional, durable and enjoyable for a long time.

We'll tell you the 10 most common mistakes when building a composting toilet and how to avoid them in our DIY fails blog article. 

Design and construction

The corpus

The body is an important part of the composting toilet. It ensures that the toilet is stable and robust. Here are some steps to consider when constructing the body:

Material: Choose the material that best suits the location and type of your toilet, is durable and can withstand external influences. Common materials are wood, metal or plastic.

Size: Measure the space where the composting toilet will be located and draw a plan to make sure everything fits. This is a very important preparation, as one or two millimetres too much or too little can lead to an unsatisfactory result afterwards.

Cutting: Cut the material into the desired sizes and shapes. Make sure that all parts are cut to the same length so that the corpus has a stable statics.

Assembly: Start assembling the cabinet. Use screws or nails to join the pieces together and make sure the carcase is stable.

Reinforcements: To make the cabinet even sturdier, you can add extra reinforcements. Corner supports or additional cross braces are suitable for this.

Check the stability: Check the stability of the cabinet. You can test this by pressing lightly against it or sitting on it carefully.

Seat and container

If you want to build a composting toilet yourself, the toilet seat, the separating insert and the containers are crucial components. They will later form the basis for correct use, separation of urine and solids and comfortable sitting when going to the toilet. Here are some important considerations when choosing:

Toilet seat: In terms of toilet seat, you have a choice between DIY or buying. Of course, it is possible to make a wooden seat and lid. You can attach it directly to the toilet with hinges. If you want to make things a little easier for yourself or want additional comfort, such as a soft-close mechanism, buying a ready-made toilet seat is the better choice.

Separators: There are different types of separator inserts to separate urine from solids. Some common options are plastic inserts, ceramic or stainless steel inserts. It is important to choose the right insert because it is the heart of your dry composting toilet. In this respect, the insert must fit and the separation of solid and liquid must work smoothly.

Need more information about separator inserts? Feel free to read our article. 

Buy or build yourself: You can either buy separation inserts and containers as ready-made components or build them yourself. The decision depends on your craftsmanship, your budget and your preference. If you are a skilled craftsman, you can build your own separation insert and match it perfectly to your composting toilet. It should be mentioned at this point that building your own using deep-drawing techniques can be quite a challenge, while the ready-made version often makes the work easier.

Tank sizes: The size of the container is measured by the number of users of the composting toilet. Larger bins are ideal for families or groups, while smaller bins are better suited for individuals. There are different bin sizes on the market, ranging from 4.5 litres to 50 litres or more.

Bin capacity: The capacity of the bin depends on the frequency of use. Some bins can hold a large number of shops, while others only have space for three or four sessions. It is important to choose a capacity that suits your needs so that the urine canister and solids container do not fill up too quickly.

Fit accuracy: Make sure that the openings of the divider fit exactly into the containers below. This way you avoid unpleasant surprises where the separation of solids and liquids does not work.

Ventilation system

If you want to increase the drying process of your self-built composting toilet, it makes sense to consider a ventilation system in your construction planning. An effective ventilation system can help minimise unpleasant odours and prevent mould.

Basically, you have various options. If you use the dry composting toilet in your summerhouse, for example, an exhaust system with a ventilation pipe makes sense. In a motorhome, on the other hand, you can use a fan or connect the toilet to your existing SOG system.

Ventilation system with exhaust pipe: A ventilation pipe is a central component of the ventilation system. It drains the air from the composting toilet and transports it out of the room. The pipe should have a diameter of at least 50 millimetres and be made of plastic or metal.

Vent: Pay attention to the placement of the vent. To allow maximum air circulation, the vent should be placed on the roof or on a wall. It is also important to protect the vent from rain and snow to prevent water from entering the composting toilet.

Filter: You can also install an air filter to minimise odours. The filter should be serviced regularly and replaced when necessary. This ensures effective ventilation.

Fan: To increase air circulation, you can install a fan in the ventilation system. This can be operated either manually or automatically. Make sure that it is powerful enough to ensure that your ventilation works optimally.

Depending on the intended use, an effective ventilation system can be an important aspect if you want to build a dry composting toilet yourself. The optimal placement of the ventilation pipe and the use of filters and fans help to reduce odours to a minimum and create a healthy, mould-free environment.

Extraction fan

If you want to build your own composting toilet for your motorhome or van, an extraction fan is the system of choice. You should consider the following points:

Power: The power of the extraction fan should be matched to the size of the composting toilet. Too low a capacity will result in insufficient ventilation, while too high a capacity will consume an unnecessary amount of energy.

Placement: Place the exhaust fan close to the ventilation pipe to ensure effective airflow.

Filter: A carbon fibre air filter can be optionally installed in the exhaust fan's ventilation system to minimise odours. The filter should be serviced regularly and replaced when necessary.

Power supply: The exhaust fan requires a power supply. Depending on availability, you can choose an electric power supply or a battery.

Urine canister and solids container

The urine and solids containers are used to collect the waste. If you want to build a composting toilet yourself, you should definitely think about purchasing the appropriate containers. In addition, it is important to choose containers that allow you to dispose of and clean them easily.

Material: The containers should be made of a durable, non-toxic and easy-to-clean material. Plastic or stainless steel are good choices.

Size: The size of your containers depends on how often you use them. A larger volume means that the container or canister needs to be emptied less often. However, in this case the containers also require more space and - when they are completely full - become significantly heavier.

Emptying: The urine canister and the solids container should be designed so that you can empty them easily. Some composting toilets have a container that can be removed from the front, others have a drainage tap or a connection for a hose to drain the urine. Another alternative is to remove the divider from the body and pull the containers out upwards. In the end, the size of the room determines your options.

Hygiene: It is important to clean the container regularly to avoid unpleasant odours and the build-up of bacteria. For effective cleaning, you should choose containers with surfaces that are as smooth as possible, that are not damaged by the use of diluted citric or acetic acid and that are also rustproof.

Design

To ensure that your composting toilet fits in perfectly with the interior of your vehicle, garden shed or Tiny House, you need to think about how the toilet should look and how you want to integrate it. You can adapt the design to the ambience of the room.

Whether it's simple and minimalist, impregnated and embellished with paints and varnishes or decorated with carvings: There are virtually no limits to your imagination. When using lacquers or varnishes, we recommend that you pay attention to environmental compatibility and durability.

Installation and use of the self-built composting toilet

What to start with and how to finish? To give you an overview of the procedure for assembling your self-built composting toilet, we have collected some important points for you.

1. Site preparation: The first step in installing a homemade composting toilet is to prepare the site. This should be well ventilated to prevent mould growth. In addition, the location must be level and stable to ensure safe installation.
2. Assembling the body: After you have drawn up your construction plan and procured all the necessary materials and tools, you start building the body. Pay attention to stability, statics and - especially in the case of vehicles - to secure anchoring in the ground.
3. Installing the divider insert: Once you have decided on a ready-made divider insert, insert it into your cabinet. If you create your own individual divider insert, you must first make it before installing it. It is important to pay attention to absolute accuracy here, too, so that the divider fits into your body and into your containers and later functions exactly as you want it to.
4. Installing the toilet seat: Once your divider insert is integrated into your toilet, you mount your toilet seat with the matching lid. If the seat is ready-made, it is attached to the body with screws. If you are building your own individual toilet seat, you must first saw out the shape and the lid from wood.
5. Inserting the containers: Now you place your urine canister and your solids container in the composting toilet. If you are using a separate tank for the urine, you must first drill a hole in the body and lead a hose to the canister.
6. Installing the exhaust fan/ventilation: If you decide to use an exhaust system, you need to install the pipe or fan hose for the exhaust air. If you are using a ventilation system with a fan, this must also be installed and connected to the electrical circuit.
7. Decoration: Once the composting toilet is fully assembled, you can start decorating its exterior.
8. First use: Before using your newly built composting toilet for the first time, it’s wise to test everything to ensure proper functionality, especially the alignment of the urine canister.

All in all, installing a self-built composting toilet requires some planning and work, but you will be rewarded with your own individual, sustainable, quiet little toilet. It is important to carry out the planning and installation carefully to avoid unpleasant surprises afterwards.

Tips for using your self-built composting toilet

Your dry composting toilet is set up and fully functional, and you're ready to start using it comfortably? Here are a few tips to make sure that the use of your toilet runs smoothly:

Use suitable litter: Not all materials are equally suitable for use in the dry composting toilet as litter for the solids. In general, it makes sense to use natural material. This is in line with the sustainability concept of the dry composting toilet. You can choose between small animal litter, sawdust, fine bark mulch, Terra Preta, litter with activated carbon or dried coffee grounds. Basically, anything that binds moisture is suitable. However, do not use conventional cat litter, as it clumps and is often contaminated with chemical additives.

Clean your composting toilet regularly: It is important to clean your composting toilet regularly so that you feel comfortable on your litter tray and counteract the formation of bacteria. Diluted vinegar or citric acid or products with effective microorganisms are particularly suitable. You can find more tips on cleaning here.

Empty the containers regularly: Fresh urine is odourless. However, if it accumulates over several days and weeks, bacteria will form, which in turn will cause odours. Therefore, you should make sure that the urine canister is emptied regularly. You can take more time when emptying the solids container. If large pieces of waste remain in the bin longer, the composting process will begin.

Dispose of your waste properly: You can use any toilet connected to the sewage system to dispose of the urine or use the urine diluted as fertiliser. The solids can be disposed of in a rubbish bag in the residual waste bin. Conditionally, composting of the solids is also possible. Here you can read about how and where solids and liquids can best be disposed of. Always observe the disposal regulations of the respective municipality or country.

Ensure good ventilation: Good ventilation is important to promote the drying process inside the composting toilet and thus prevent odours. In addition, you prevent the formation of mould.

FAQs on the subject of building a composting toilet yourself

Which material is best if I want to build a composting toilet myself?

There are different materials that are well suited for building a dry composting toilet. The choice of material depends on several factors, such as location, durability and budget. Here we present several options:

Wood: In most cases, wood is the material of choice if you want to build a composting toilet yourself. It is readily available, easy to work with and has a natural look. However, wood can be damaged by moisture and mould.

Plastic: Plastic is a robust and durable material option that is resistant to moisture and mould. It is also easy to clean. However, plastic can be limited in its aesthetics and can become brittle due to sun exposure.

Metal: Metal such as stainless steel is a durable and hygienic material for building a composting toilet. However, it is more expensive than other materials and can be prone to corrosion if not cleaned properly.

Concrete: Concrete is a robust and durable material option that is resistant to moisture and mould. However, it is heavy and difficult to transport. This eliminates this option for vehicles.

Ceramic: Ceramic is a hygienic, durable and easy to clean material. However, ceramic is more expensive and heavier than other materials.

In summary, each material has advantages and disadvantages. It is important to check these with regard to your location and your individual needs and thus find the material for your composting toilet that best suits you and your needs.

How much time should I allow if I want to build a composting toilet myself?

The time it takes to build a composting toilet is as individual as your quiet place and depends on various factors, such as the material, size, comfort level and personal craftsmanship.

If you want to build a composting toilet yourself, you are deciding on a project, not an entertaining Saturday afternoon activity. Building a dry composting toilet can take several days to weeks. If you choose a mixture of DIY and self-bought components such as a divider, toilet seat with lid and/or containers, the construction time is usually shorter.

It is important to be realistic about your project and your skills and to plan enough time. It is better to have a buffer than to go on holiday with a half-finished and therefore unusable dry composting toilet on board.

Do I need special knowledge or skills to build a composting toilet myself?

Building a composting toilet requires a certain degree of craftsmanship and technical understanding. If you have a wealth of experience in these areas, the construction will certainly be easier for you. But even if you're a toilet-building novice, it's possible, with good preparation, patience (and perhaps the help of friends), to create the toilet of your choice yourself.

Here are some skills and knowledge that can be useful when building a composting toilet:

Spatial imagination: if you want to build a composting toilet yourself, you should be able to plan the toilet and create the design so that the composting toilet meets your needs and requirements, fits into the space and works after construction.

Woodworking: Basic woodworking skills are helpful to build the body and possibly the toilet seat along with the lid.

Understanding of electronic circuits: If you want to attach your composting toilet to an electrical ventilation system, it is an advantage if you have a technical electronic understanding.

Tool skills: In order to know which tool to use for which step, you should also have some prior knowledge.

If you are not sure whether your skills and knowledge are sufficient to build a composting toilet yourself, you also have the option of looking for a ready-made version. You will find many different models and sizes here. Maybe there is a suitable one for you here. ;)

Conclusion: Should I build a composting toilet myself?

The decision whether you should build a composting toilet yourself depends on various factors, such as your skills, your budget, your time resources and your needs. In general, the DIY version of the environmentally friendly toilet is cheaper than prefabricated models and, of course, more individual.

However, the construction requires a certain degree of craftsmanship and technical understanding. It is important to be realistic in assessing your skills and resources and to plan carefully so that your "build your own composting toilet" project is a complete success.