Quick answer: a separating composting toilet keeps liquids and solids apart. Urine goes forward into a canister you pour out; solids drop into a lined container with a scoop of litter and dry out. No water, no chemicals, no black tank, no hookup. For a van or a tent, the small Trelino Evo S or Origin S fits almost anywhere. For an RV, a cabin or a tiny home where you want a normal seat height and fewer emptying trips, the L sizes are the ones to look at.
How the separator works
Lift the lid of a Trelino and you see a seat insert with two openings. The front one is a funnel that sends urine into a canister. The back one drops straight into a solids container lined with a bag. Because the two never mix, nothing starts to ferment. You cover each solid use with a cup of coconut coir, fine wood shavings or sawdust, and the litter pulls the moisture out.
That is the whole trick. Odor in a portable toilet comes from liquid and solid waste sitting together. Separate them and keep the solids dry, and there is nothing to smell. The small sizes do not even need a fan; the larger ones take an optional one for long trips or several users.
Emptying
The urine canister comes out through the top. Trelino's guidance is to empty it every 3 to 4 days at the latest, into any toilet connected to a sewer, then rinse with vinegar diluted 1 to 7 so no scale forms. A membrane in the canister lid lets urine in and stops it sloshing back out on a rough road.
The solids container holds a bag. When it is full, tie the bag off and put it in the household trash, the same as diapers or pet waste. With compostable bags and compostable toilet paper, home composting is possible where local rules allow it. The small sizes hold roughly 4 to 8 uses, the large ones 11 to 20.
Evo or Origin
Trelino makes two lines in three sizes each. They work the same way inside.
- Evo has an ABS body and polypropylene containers, a soft-close lid attached to the seat, and comes in white or dark gray. It is the lighter line: the Evo S is 8.6 lb. The lid is thin by design and is a lid, not a seat.
- Origin has a polyethylene body with a glued multilayer birch wood lid held shut by magnets. It is a few pounds heavier and looks like furniture.
Which size
| Model | Size, W x D x H | Weight | Urine canister | Solids container | Fan |
|---|---|---|---|---|---|
| Evo S | 13.0 x 15.4 x 11.7 in | 8.6 lb | 1.2 gal, 9 to 11 uses | 1.6 gal, 4 to 8 uses | Not needed |
| Evo M | 13.0 x 15.4 x 14.2 in | 9.5 lb | 1.3 gal, 9 to 11 uses | 2.1 gal, 6 to 12 uses | Optional |
| Evo L | 13.0 x 15.4 x 16.9 in | 10.8 lb | 2.6 gal, 12 to 22 uses | 2.6 gal, 11 to 20 uses | Optional |
| Origin S | 13.6 x 15.7 x 11.2 in | 11.9 lb | 0.9 gal, 7 to 10 uses | 1.6 gal, 4 to 8 uses | Not needed |
| Origin M | 13.0 x 15.4 x 13.2 in | 12.8 lb | 1.3 gal, 9 to 11 uses | 1.8 gal, 5 to 10 uses | Optional |
| Origin L | 13.0 x 15.4 x 18.1 in | 15.0 lb | 2.6 gal, 12 to 22 uses | 2.6 gal, 11 to 20 uses | Optional |
Van, small camper, boat or tent: the S sizes. The Evo S at 8.6 lb is the one to carry in and out; the Origin S is the one to leave in place with a wood lid you do not mind looking at.
Sprinter van, truck camper or trailer with two people: the M sizes. More capacity, a taller seat, and a fan if you want it.
RV, skoolie, cabin, garden office or tiny home: the L sizes. The 16.9 and 18.1 in heights sit like a household toilet, and 2.6 gal containers mean fewer trips. Add the SOG TT fan set on 12 V when several people use it.
What to add
- A second urine canister, so you can swap and keep going: 2.6 gal for L models, 1.3 gal for M models.
- Bags: recycled bags for the trash, biodegradable bags for composting.
- A Urinometer, a float that lifts an orange arrow when the canister is nearly full.
- A travel plug for the Evo or the Origin, so a half-full canister rides along sealed.
- Membrane spares, replaced every 3 to 6 months.
All of it is in our Composting Toilets collection. Trelino drop-ships from its US stock, and orders over $250 ship free in the contiguous US.
Questions we get
Does it really not smell?
Not in normal use. Separation plus dry litter is what every separating toilet relies on. If it ever does, the usual cause is a wet solids bin: add more litter and empty sooner in hot weather.
What about winter?
There is no water in the toilet, so the body cannot freeze. Empty the urine canister before a freezing night.
Can two people use an S size?
Yes for a weekend. For full-time use by two people, an M or L means emptying every few days instead of every day or two.
Does it need power?
No. Only the optional fan set uses power, 1.2 W on 12 V.
Can I install it permanently?
Yes. The manual covers fixing it down so it cannot tip in a moving vehicle.