One of our customers, Matyas, recently sent in photos of the composting toilet he built for his campervan around our Complete Urine Separator — and left a lovely five-star review calling it "one of the cheapest ways to make a composting toilet." He's not wrong. So we thought we'd walk you through how a build like his comes together, because if you can use a jigsaw and a screwdriver, you can make one too.
The whole idea is simple. A composting toilet doesn't need a tank, plumbing or chemicals. It needs two things working together: a way to keep urine separate from solids (that's what stops the smell), and a bit of airflow to keep everything dry. Get those two right and the rest is just a box to sit on.
What you'll need
Matyas kept it lean, and you can too. You'll want a Complete Urine Separator, a standard toilet seat, a sheet of plywood for the top and base, a few lengths of softwood batten for the uprights, and some thin flexible board or plastic to wrap around as the outer skin. Add a 25-litre bucket or a urine bottle underneath, a length of 1¼" push-fit waste pipe, and a small 12V extractor fan if you're fitting it in a van.
Building the frame
Start with the carcass. Cut an oval top and a matching base from plywood, then join them with short timber uprights to make a sturdy drum-shaped frame — Matyas spaced his evenly all the way round so the whole thing stays rigid. Cut the hole in the top to suit the oval of your toilet seat. This frame is the skeleton; it carries your weight and holds everything in position.
Cladding and the seat
Next, wrap the outside. A thin sheet bent around the frame and screwed to the uprights gives you that clean, curved finish you can see in Matyas's build — and it hides the bucket neatly inside. Sit your separator under the toilet seat so the funnel lines up with the opening, and screw the seat platform down onto the top. Our Complete separator fills the full oval of a standard seat, with a rear opening that drops solids straight into the bucket and keeps the inside clean.
The bit that does the magic
Connect the separator's 35mm outlet to 1¼" push-fit pipe and run it down to a bottle or container. Urine goes one way, solids drop into the bucket the other. That separation is the single thing that makes a composting toilet pleasant to live with rather than something you dread. In a van, add a small extractor fan — exactly as Matyas did — to pull a gentle draught through and keep solids drying out between uses.
And that's it
No mains water, no black tank, no chemicals — just a clever bit of plastic, some plywood and an afternoon in the workshop. Every separator is handmade in Wales from solid 4mm ABS, built on over 20 years of getting the shape exactly right for both men and women.
If you fancy building your own, you'll find the Complete Urine Separator here, or browse the full range in our urine separators collection. And if you build one, send us a photo — we love seeing where they end up.
