A composting toilet is built in either of two ways: a 20-litre bucket under a seat that is carried out and emptied into an outdoor bin, or two sealed chambers of about 1 cubic metre each that take turns filling and resting. A urine diverter can be added to either, and the seat height and floor layout can be changed so a wheelchair user can transfer to it. Start with the bucket system because it is the cheapest to build and the easiest to correct.
Part of Composting Toilet Systems
A waterless toilet collects human waste on a bed of dry carbon cover instead of flushing it away. The design choice is where the waste is held and how it gets to the compost pile.
Every Design Does The Same Four Things
- Takes the waste without water. A seat over a container, with a lid.
- Covers every deposit. Dry carbon (sawdust is ideal) hides it, soaks up moisture, blocks odour and stops flies.
- Moves the waste to composting. Either the bucket is carried to a bin or the chamber is sealed and left to rest.
- Keeps a hand-washing station next to it. Soap and water, or ash and water. The parent page calls this non-negotiable.
The Four Designs At A Glance
| Design | What it is | Best when | Main trade-off |
|---|---|---|---|
| Simple bucket system | 20 L food-grade bucket in a plywood box, emptied to a bin | You need a toilet this week; few people; renting or moving | Someone must carry and empty buckets often |
| Dual-chamber (batch) | Two masonry chambers, about 1 m × 1 m × 1 m each | A permanent home and a steady household | More building; chamber size decides how long waste rests |
| Urine-diverting | A separator at the front of the seat sends urine to a container | Add to either design to keep the solids drier | Urine pipes clog if not kept short and rinsed |
| Wheelchair-accessible | A lower seat, level access and turning room | Anyone who cannot climb steps or squat | A raised batch chamber needs a long ramp |
Where The Pile Is Made
The toilet only collects. The composting happens somewhere else:
- In the bucket system the waste is tipped into an outdoor bin built for it (Compost Bin Construction).
- In the dual-chamber system the waste composts in place while the other chamber fills.
In either case the pile must be treated as human waste until heat and age have been verified (Pathogen Kill Requirements).
Choosing
- Need it now, or unsure how long you will stay? Bucket system.
- Staying and have masonry skills and materials? Dual-chamber, sized to give each chamber enough resting time (Chamber Sizing).
- Anyone with limited mobility in the household? Plan the accessible layout first; it is far harder to retrofit.
- Wet site or high water table? Keep everything above ground; a composting toilet needs no pit, which is why it suits sites where a pit latrine would reach groundwater.
Common Mistakes
- Building before stockpiling cover. Running out of sawdust is the usual cause of smell and flies.
- Sending any liquid from the toilet into the greywater system. Toilet waste and whatever drains from it belongs with the compost, not with wash water (Greywater vs. Blackwater).
- Skipping the hand-washing station. The toilet then works and the household is still infected through hands.
Safety
The toilet, bucket and chambers hold human faeces
Handle with gloves, wash hands afterwards, keep chambers sealed and vented, and never climb into a chamber. A closed vault can hold gases that are toxic and flammable, and the smell is not a reliable warning. Empty only material that has rested for the full time.
What’s Next
- Learn next: Simple Bucket System — build the first toilet
- Combine with: Cover Materials & Management — the supply that keeps any design working