How to Build a Composting Toilet

Are you seeking an eco-friendly bathroom solution that saves water and creates valuable compost? You’ve come to the right place! After helping dozens of homesteaders and off-grid enthusiasts build their composting toilets, I’m excited to share everything you need to know about creating your sustainable bathroom setup.

What Is A Composting Toilet?

A composting toilet is an eco-friendly alternative to traditional flush toilets that transforms human waste into usable compost through natural decomposition processes. Unlike conventional toilets that use gallons of water with each flush, composting toilets require little to no water, making them perfect for off-grid living, tiny homes, or anyone looking to reduce their environmental footprint.

The magic happens when microorganisms break down waste in an aerobic environment (with oxygen), turning it into nutrient-rich compost that can eventually be used in your garden – though I recommend using it only for non-edible plants!

I remember when I first installed my composting toilet at my weekend cabin. The water savings alone were remarkable – nearly 6,000 gallons per year compared to my city home. That’s when I became a true believer in this sustainable solution.

What are the Different Types of Composting Toilets?

Before diving into the building process, it’s essential to understand your options. Composting toilets come in two main varieties:

Split or Central Composting Toilets

Split systems separate the toilet fixture from the composting chamber. When you use the toilet, waste travels to a separate composting unit, typically located beneath the bathroom (like in a basement) or outside the building. These systems are ideal for permanent installations in homes with suitable spaces for the composting chamber.

The main advantage? The composting happens away from your bathroom space, which means more room and potentially less odor in your bathroom area.

Self-Contained Composting Toilets

Self-contained units keep everything in one compact package – the toilet seat and composting chamber are integrated. These are perfect for smaller spaces, temporary setups, or situations where you can’t install a separate composting chamber.

While commercial self-contained units can cost $1,000 or more, building your DIY version can save you hundreds and give you the satisfaction of creating something functional with your hands.

What are the Steps of Making a Composting Toilet?

Ready to build? Let’s break down the process into manageable steps. I’ll focus on creating a self-contained composting toilet with a urine separator, one of the most effective and odor-free designs.

Gathering Your Materials

First, collect everything you’ll need:

• Plywood (¾-inch is ideal) for the box
• A standard toilet seat
• A urine separator (can be purchased online or made from plastic containers)
• A 5-gallon bucket for solid waste
• A smaller container for urine collection
• PVC pipe (2-inch diameter) for ventilation
• A small computer fan or dedicated composting toilet fan
• Absorbent material (peat moss, coconut coir, or sawdust)
• Basic tools: drill, saw, screws, and measuring tape

Building the Toilet Box

1. Cut your plywood to create a box approximately 18 inches wide, 19 inches deep, and 18 inches tall.
2. Use pocket holes or wood glue and screws to secure the pieces together.
3. Design the box with an opening on top for the toilet seat and a front access panel to remove the waste bucket.

Drilling the Vent Hole and Attaching a Vent

Proper ventilation is crucial for a smell-free experience:

1. Drill a 2-inch hole in the back or side of your toilet box.
2. Insert the PVC pipe into this hole.
3. Extend the pipe upward and outside through a wall or window.
4. Install a small fan in the pipe to create negative pressure, pulling air from the toilet and expelling it outside.

I learned that skimping on ventilation is a recipe for disaster. When I built my first composting toilet, a simple passive vent would be enough. Boy, was I wrong! Adding a small computer fan made all the difference between a pleasant experience and an unpleasant one.

Installing the Urine Separator

Separating liquids from solids is perhaps the most critical factor in preventing odors:

1. Place your urine separator at the front of the toilet box opening.
2. Create a path for urine to flow into a collection container.
3. Ensure the separator slopes toward the collection container.
4. Make sure the separator sits slightly higher than your solid waste bucket.

Setting Up the Toilet Seat

1. Position your toilet seat over the box opening, ensuring it aligns appropriately with the urine separator.
2. Mark and drill holes for the toilet seat mounting brackets.
3. Attach the seat securely to the box.

Adding a Divider Panel and the Front Wall

1. Install a divider panel inside the box to separate the solid waste bucket from the urine container.
2. Create a front access panel that can be easily removed when emptying either container.
3. Add hinges or latches to keep the panel secure but accessible.

Adding Absorbents

Before using your new toilet:

1. Place your 5-gallon bucket beneath the toilet seat opening.
2. Add about 2 inches of absorbent material to the bottom of the bucket.
3. Keep a small container of extra absorbent material nearby with a scoop.

After each use, add a small scoop of absorbent material to cover the waste. This helps absorb moisture, reduce odors, and begin the composting process.

Securing the Toilet Seat Lid

Don’t forget to attach the toilet seat lid! This helps contain potential odors when the toilet isn’t used and gives your DIY project a finished look.

Cutting Out the Toilet Seat Hole

If your plywood top doesn’t already have an appropriate opening:

1. Trace the inner outline of your toilet seat onto the top of the box.
2. Use a jigsaw or similar tool to cut out the hole.
3. Sand the edges smooth to prevent splinters.

What are the Drawbacks of a Composting Toilet?

While composting toilets offer numerous benefits, it’s essential to be aware of potential challenges:

1. Regular maintenance: Unlike flush-and-forget conventional toilets, composting toilets require emptying containers and managing the compost.
2. Learning curve: Finding the right balance of absorbent materials and managing moisture levels requires some trial and error.
3. Space requirements: Even self-contained units occupy more space than a traditional toilet.
4. Social acceptance: You should explain how composting toilets work to guests who are unfamiliar with them.
5. Regulations: Some areas have specific codes regarding human waste management, so check local regulations before installing them.

How Much Does It Cost to Build a Composting Toilet?

One of the biggest advantages of building your composting toilet is the cost savings. While commercial composting toilets can cost from $1,000 to over $3,000, a DIY version typically costs between $100 and $300, depending on the materials you choose and what you might already have on hand.

Here’s a rough breakdown:

• Plywood: $30-50
• Toilet seat: $20-40
• Urine separator: $30-60 (or make your own for less)
• 5-gallon bucket: $5-10
• Ventilation supplies: $20-50
• Miscellaneous hardware: $10-30
• Initial supply of absorbent material: $10-20

What is the Best Material to Use in a Composting Toilet?

The right covering material makes all the difference in a successful composting toilet. Here are the top options:

Coconut coir: This sustainable byproduct of coconut processing is my personal favorite. It absorbs moisture, controls odors well, and breaks down nicely. It’s also lightweight and expands significantly when water is added.

Peat moss: A traditional choice that works well but comes with environmental concerns since peat bogs are slow to regenerate.

Sawdust: Specifically, hardwood sawdust (avoid treated wood) works well and might be free if you know a woodworker or have a local sawmill.

Wood shavings: Similar to sawdust but with larger pieces that create more air space in the compost.

Dried leaves: Shredded fall leaves work surprisingly well and cost nothing if you have deciduous trees nearby.

I’ve experimented with all these materials, and coconut coir consistently provides the best balance of performance, availability, and environmental impact. It’s worth the slightly higher cost compared to other options.

Conclusion

Building your composting toilet is a rewarding project that can save water, reduce environmental impact, and provide valuable compost for your garden. While it requires some initial effort and ongoing maintenance, many users (myself included) find that the benefits far outweigh the drawbacks.

Remember that your first design might not be perfect – that’s okay! Feel free to modify and improve your setup as you learn what works best for your situation. The key is starting with good ventilation and effective liquid/solid separation.

Ready to give conventional plumbing a break and embrace a more sustainable bathroom solution? Grab your tools and get building – your garden and the planet will thank you!

Also Read: How Much Does It Cost to Build a Robot?

FAQs