If you want a DIY composting toilet you can build yourself, this guide walks you through a simple, low-cost design that separates urine from solids, controls odor with dry cover material (like sawdust), and stays easy to empty and clean.
You’ll get a clear materials list, build dimensions guidance, step-by-step instructions, and the real-world build nuances DIYers usually discover mid-project: alignment, moisture control, sealing, and odor-proofing.
This project is ideal for cabins, tiny homes, workshops, and off-grid setups where saving water matters and plumbing is inconvenient (or nonexistent).
⚠️ Safety Note: Human waste can contain pathogens. Follow local regulations for composting toilet waste handling and disposal. Use basic hygiene and PPE habits (gloves, handwashing, dedicated tools) when emptying or cleaning.
What Is A DIY Composting Toilet And Who Is This Build For?
A DIY composting toilet is a waterless toilet that separates liquids from solids and uses a carbon cover material (like sawdust) to reduce odor and support decomposition. This build is best for DIYers who want a simple, bucket-based system for cabins, tiny homes, off-grid spaces, and workshops.
A composting toilet doesn’t “flush waste away.” Instead, it manages waste on-site using three core ideas:
- Separation: urine goes one way, solids go another (this is huge for odor control).
- Carbon Cover Material: a dry “bulking agent” (sawdust, coconut coir, dry leaves) goes over solids after each use.
- Air + Dryness: keeping the solids container relatively dry prevents stink and flies.
Who This Build Fits Best
- You want a straightforward DIY project that’s beginner-friendly.
- You can empty containers periodically (urine more often than solids).
- You can store dry cover material nearby.
- You want low complexity (no fancy internal agitators required).
Who Should Consider A Different System
- You want “set it and forget it” indoor convenience.
- You need a system compliant with specific building codes (some locations require certified units).
- You want a large compost chamber that processes for long periods in-place.
What Materials Do You Need for DIY Composting Toilet?
To build a DIY composting toilet, you need a sturdy box (plywood), a toilet seat, a urine diverter, one liquid container, multiple 5-gallon buckets for solids, and a dry carbon cover material like sawdust. You can substitute materials as long as the structure is stable and the cover material stays dry.
Core Materials
- Plywood (Recommended 3/4″): For the toilet box (top, sides, front/back, internal supports).
- 2×4 Lumber: For legs and/or internal bracing.
- Toilet Seat: Sturdy and comfortable (standard size is easiest).
- Urine Diverter (Urine Separator): The MVP of odor control.
- Containers
- Solids: Standard 5-gallon bucket(s) (have at least 2 to 3 for rotation).
- Liquids: A long/narrow container or jug that fits under the diverter spout (easy to remove).
- Cover Material (Carbon Bulking Agent)
- Best: kiln-dried sawdust, fine wood shavings, or coconut coir
- Also works: dry leaves (crumbled), peat moss (where appropriate), shredded paper (less ideal if it clumps)
- Fasteners
- Wood screws (assorted)
- Small bolts/screws for seat hardware (as needed)
- Finish
- Paint, stain, or sealant (choose a finish that tolerates moisture and cleaning)
Optional But Strongly Recommended
- Hinges for an access lid/top
- Magnetic catch or latch to keep the lid shut
- Weather stripping / foam gasket tape to improve sealing
- A small vent fitting + hose (or a passive vent path) for better odor control
What Tools Do You Need for a DIY Composting Toilet (And What You Can Skip)
You can build a DIY composting toilet with basic tools like a saw, drill, measuring tape, and jigsaw for the seat opening. A pocket hole jig is helpful, but you can also use brackets or pre-drill and screw into framing.
Essential Tools
- Measuring tape + pencil
- Saw (circular saw, table saw, or handsaw)
- Drill + drill bits
- Jigsaw (for the toilet seat opening)
- Screwdriver or driver bit
- Sandpaper or file (smooth edges)
Helpful Tools
- Pocket hole jig (clean joins, strong box)
- Clamps (makes assembly calmer and straighter)
- Hole saw (for vent openings if you add venting)
What You Can Skip
No need for fancy joinery tools if you build with basic screws + internal 2×4 bracing.
DIY Composting Toilet Dimensions, Seat Height, And Cut List
A comfortable DIY composting toilet usually targets standard chair-like toilet height and must fit both a solids bucket and a urine container without tipping or pinching. Planning dimensions first prevents common problems like urine misalignment, cramped bucket removal, and hard-to-clean corners.
This is where most DIY composting toilet projects either become elegant… or become “the cube that hates you.”
Seat Height Target
Aim for 16 to 18 inches from floor to seat rim (typical comfort range). If you prefer a more “squat-friendly” posture, go slightly lower. If you want easier sit/stand, go slightly higher.
Key Interior Fit Rules
- Solids bucket must slide in/out without wrestling. Leave a little clearance on the sides (think “smooth removal,” not “perfectly wedged”).
- Urine container must be easy to remove without bumping the bucket.
- The diverter must align so liquids don’t splash into solids (or onto your wood).
Practical Sizing Approach (Simple And Reliable)
- Choose your solids bucket and urine container first.
- Place them on the floor in the arrangement they’ll sit under the seat.
- Add space for:
- bucket removal
- lid hinges
- diverter mounting
- Build the box around that reality.
Cut List Guidance (Use Your Measured Dimensions)
Because urine diverters and container shapes vary, the best cut list is the one built from your actual buckets.
But your box generally needs:
- Top panel (seat opening cut into this)
- Bottom panel (optional, but helps stability)
- Left and right side panels
- Front panel
- Back panel
- Internal rails/bracing (to support the top and guide buckets)
Pro Tip: Before final assembly, do a “mock fit” with the diverter installed and the containers in place. If something is off now, it will be off forever.
How To Build A DIY Composting Toilet (Step-By-Step)
Build the box first, then cut the seat opening, install the urine diverter, and test-fit both containers before final screws. The most important detail is alignment: solids must drop cleanly into the bucket and urine must flow into the liquid container without splashing or leaks.
Step 1: Build The Box Frame
- Cut your panels based on your measured bucket layout.
- Assemble the box using screws (and internal 2×4 bracing if needed).
- If you want a clean look: pocket holes. If you want a rugged look: screws + bracing.
💡 Build Nuance: Don’t permanently attach the top yet. You’ll want access during fitting.
Step 2: Plan And Cut The Seat Opening
- Place the toilet seat on the top panel.
- Trace the inside rim opening.
- Cut slightly larger than your trace so the opening doesn’t pinch and is easy to clean.
💡 Sand the cut edge until it’s smooth (splinters are not part of the sustainability plan).
Step 3: Install The Urine Diverter
- Mount the urine diverter beneath the front portion of the seat opening (per its design).
- Ensure the diverter spout points cleanly into the urine container.
💡 Build Nuance (Alignment Test): Before screws become permanent, simulate positioning:
- Put the urine container under the spout
- Confirm it can be removed without hitting the bucket
- Confirm the spout won’t drip onto wood
Step 4: Add Bucket Guides And Access
- Place the solids bucket in position.
- Add simple guide rails (wood strips) so the bucket returns to the same spot every time.
- Make sure the top can open easily:
- hinges on the back, or
- a removable top panel section
💡 Build Nuance: A small gasket strip (foam tape) where the lid meets the box helps odor control and keeps the top from rattling.
Step 5: Attach Legs And Waterproof The Build
- Add 2×4 legs at each corner (or build a simple base frame).
- Check stability: no wobble allowed.
- Seal or paint the wood to resist moisture and simplify cleaning.
💡 Build Nuance: Waterproofing is not vanity. It’s “future-you will thank you” in liquid-resistant handwriting.
Step 6: Choose Buckets And Set Up Rotation
- Solids: keep 2 to 3 buckets so you can swap quickly.
- Liquids: choose a container you can pour easily and clean quickly.
Label them if needed. A tiny bit of organization prevents awkward surprises.
Step 7: Add Cover Material Station
Keep a container (small bin with scoop) next to the toilet. After every solids use, add enough cover material to fully cover the deposit.
Best Practice: If odor appears, you usually need:
- More cover material
- Drier cover material
- Better urine separation
How Does A Composting Toilet Work?
A DIY composting toilet works by separating liquid waste (urine) from solid waste using a urine diverter. Solids fall into a bucket and are covered with carbon-rich material like sawdust to promote aerobic decomposition and eliminate odors. Urine is diverted into a separate bottle to prevent sewage smells and maintain the correct moisture balance.
Before you pick up a saw, it is crucial to understand the biological process and how a composting toilet works. Standard flushing toilets mix waste with water, creating sewage.
A composting toilet does the opposite: it separates waste to facilitate nature’s decomposition process.
The Solids: These go into a 5-gallon bucket. To prevent smell, they must be covered immediately with “bulking material” (sawdust, peat moss, or coco coir). This adds carbon, which heats up the pile and breaks down pathogens.
The Liquids: Urine contains high nitrogen and, when mixed with feces, causes the classic “sewer smell.” By using a urine separator to funnel liquid into a jug, you keep the solids dry and odorless.
How To Keep A DIY Composting Toilet From Smelling
Most odors come from excess moisture, poor urine separation, or not enough dry cover material. Keep the solids bucket dry, add cover material after every use, and improve sealing or airflow if smells persist.
The Odor Triangle (Break Any Side, Win)
- Moisture (too wet)
- Exposure (bucket open to air gaps)
- Mismatch (not enough carbon cover)
Odor Control Checklist
- Add cover material every time solids are used.
- Keep cover material bone-dry (store it sealed).
- Ensure urine diverter alignment is correct.
- Add a gasket seal around the lid.
- If smells linger, consider a vent path.
Quick Fixes
- Ammonia smell: urine is hitting solids or pooling somewhere it shouldn’t.
- Sour/rot smell: bucket too wet or not enough carbon cover.
- Persistent smell despite cover: lid leaks, alignment issues, or airflow needed.
Common Composting Toilet Build Mistakes And How To Fix Them
Mistake 1: The Urine Diverter “Sort Of” Lines Up
Fix: Reposition it until urine flows cleanly into the liquid container with no splashing.
Mistake 2: Bucket Removal Requires Yoga
Fix: Add clearance. Trim internal rails. Use a hinged lid for easier access.
Mistake 3: The Lid Leaks Air
Fix: Add foam gasket tape or weather stripping. Use a latch to pull it closed.
Mistake 4: The Seat Opening Is Too Tight
Fix: Enlarge slightly and sand smooth. Make cleaning easy, not impossible.
Mistake 5: No Plan For Cover Material Storage
Fix: Add a sealed bin and scoop next to the toilet.
Frequently Asked Questions (FAQ)
Yes, you can make your own composting toilet. A composting toilet is easy to build with a few basic hand and battery tools. All you need are a few sheets of thick plywood, a toilet seat assembly, screws, and a bucket with the absorbent material. You can even create a simpler unit by using a medical toilet seat.
Yes, you can pee in a composting toilet. In that case, you’ll have to use more absorbent material, like sawdust, to neutralize the odor, as urine and feces also smell much worse together. Sawdust is rich in carbon and you need more of it to balance the extra nitrogen content, so composting can take place.
No, composting toilets don’t smell bad. If you follow the instructions and make sure there is enough absorbent material in the bucket you won’t have to deal with bad smell. If you want to be extra sure, you can install a vent with a small 12V computer fan that activates every time you open the lid.
Yes, you can use human feces for compost. Keep in mind that it’s much easier to compost feces from a toilet with a urine separator. While some municipalities recommend using this type of compost only for flower beds, if you use a hot compost heap, you can use it on your vegetable patch safely as well.
You can get rid of composting toilet waste by emptying it onto your outdoor compost bin. If you used plenty of damp sawdust or peat moss, the bucket won’t smell bad, and you can rinse it with a garden hose, dry it, and spray it with vinegar. No chemical cleaners needed.
Yes, you normally use toilet paper with a composting toilet. Toilet paper won’t decompose as quickly as feces so it will be visible long after the matter has broken down. You can use any type of paper, but keep in mind that marine and RV paper will compost the quickest. You should never throw diapers, wipes, and tampons in a compost bin.
You can dump a composting toilet on your composting heap or apply it directly to your garden. Between November and April you shouldn’t apply compost to your plants, so dump the content of your bucket into a composting bin or heap. In warmer months, empty the toilet directly at the base of shrubs and flower beds.
No, you don’t need electricity for a composting toilet. The best thing about compost toilets is that they can be used off-grid, with zero power, emissions, and pollution. If you use one in your home and want to eliminate any chance of bad odor, you can use a small 12V computer fan for venting.
Yes, earthworms can eat human waste. They live off any organic matter that is composting. When given human excrement, they will digest it and convert the remaining material into their excrement, called worm castings. Worm castings are among the best balanced natural plant foods there is.
You can make a compost toilet not smell by making sure there’s always enough absorbent material in the bucket. For this, you can use hardwood sawdust, dried peat moss, dry leaves, or coconut coir. You can also install a small computer fan to vent any lingering odors outside.
In a composting toilet, you don’t actually use conventional dirt. Instead, you add a carbon-rich material, such as sawdust, coconut coir, peat moss, or wood shavings, to aid in the composting process and to reduce odors by balancing the carbon-to-nitrogen ratio.
Yes, a urine diverter is highly recommended for a composting toilet. It separates urine from solid waste, reducing moisture and odor, which facilitates the aerobic composting process and improves the efficiency and hygiene of the system.
For a composting toilet, you’ll need a container for waste, a urine diverter, a ventilation system, a cover material like sawdust or peat moss, and possibly a composting agent to accelerate decomposition. Tools for assembly and personal protective equipment for handling waste are also essential.
The frequency of emptying a composting toilet varies depending on usage and size, but typically, the solid waste compartment needs to be emptied every 1-4 weeks. Regular maintenance ensures optimal composting and prevents odors.
Yes, you can put coffee grounds in a composting toilet. They are a beneficial addition, providing nitrogen to the composting process. However, they should be used sparingly to maintain the right carbon-to-nitrogen balance and to avoid excess moisture.
Yes, you can use biodegradable kitty litter, such as those made from wood pellets or paper, in a composting toilet. They help absorb liquids and control odor. However, avoid clumping or clay-based litters, as they don’t break down well in the composting process.
Final Notes: Should You Build A DIY Composting Toilet
This DIY composting toilet design works best where you can empty containers safely and keep cover material dry. The best upgrades are a vent fan/stack, better seals, and a more ergonomic urine diverter setup for consistent separation.
Best Places For This DIY Composting Toilet
- Off-grid cabins
- Tiny houses (depending on regulations)
- Workshops and sheds
- Temporary builds and weekend projects
Best Upgrades After You Test It
- Better sealing (gasket + latch)
- Ventilation (passive vent stack or small fan)
- More ergonomic diverter (better aiming, less splash)
- Easier cleaning surfaces (liners, removable panels, wipeable finishes)
If you build it, test it, and adjust alignment and sealing early, you’ll end up with a DIY composting toilet that feels surprisingly normal, uses zero water, and doesn’t announce itself to the entire property.
