The BioTioo does not have a second water circuit to prevent urine scale, and it doesn’t need one. Two bases and a high separating ridge prevent urine from flowing back or standing in the bowl, exactly where minerals would otherwise crystallize. Any residue that does form is removed through a fully disassemblable urine path and suitable materials, not through a second system that requires maintenance itself.
Geometry against stagnation, not water against limescale
Urine scale forms when urea in urine breaks down into ammonia, raising the pH and causing dissolved minerals to precipitate. This happens where urine stands for longer periods: at the tank bottom, sealing surfaces, and the outlet of the separating insert. A flushing toilet adds limescale from the water supply with every flush, but the BioTioo uses no flushing water and has no water connection. This already removes half of the reaction partner.
The other half we solve through shape, not chemistry. The bowl has two integrated bases as seat supports and a high separating ridge, so urine does not flow back or stand even when tilted. This is exactly where limescale would first crystallize due to stagnation. We combat urine scale at the source, through geometry that prevents it from forming in the first place, rather than washing it away afterward.
Why we don’t flush with water against limescale
An active flushing system that sprays water and a mild cleaner into the funnel every time the lid closes might sound like a more thorough solution. In reality, it just shifts the problem: a water tank with pump, tubing, and nozzle is itself a standing, moist environment that can calcify and become contaminated, especially because it is warm and repeatedly wetted. Pumps and tubing usually cannot be disassembled, only flushed through, not mechanically cleaned. In winter, there is also a frost risk: if water remains in the pump or tubing, freezing can burst the components, so the system must be emptied before cold weather.
For this reason, we decided against a second active system and instead chose disassemblability as a design principle. A component that you can completely take apart and clean under running water beats a system that must run continuously as a preventive measure to function.
The disassemblable urine path as a design principle
Accessibility is the only long-term solution against deposits. Every part of the urine path can be removed and washed, from the separating insert to the canister. The central component is the SmellX odor trap: a floating ball instead of a membrane, because rubber ages or sticks over time and then can no longer be cleaned, only replaced. The ball, on the other hand, is a smooth, mechanical part without wear parts—you wash it off and reset it. The functional principle is explained in the odor trap with floating ball.
Two surfaces are critical: the ball and its seat. A rough mineral layer prevents a clean seal, and a leaky trap lets odors escape from the tank back into the room.
Materials and cleaning chemistry
Stainless steel in the housing and PP-C in the urine path tolerate citric acid and vinegar without problems; we test both materials on our own devices in production in Überlingen on Lake Constance. Why we use exactly this combination is explained in stainless steel and PP-C. The material itself does not make the system completely limescale-free: stainless steel reduces how strongly minerals adhere to the smooth, seamless surface but does not prevent precipitation itself. How much residue forms depends further on water hardness and usage intervals, not just the housing.
An advantage is that residue on bare stainless steel is immediately visible as a fine, light film. This is not a cosmetic flaw but a sign you can wipe away before it sets. In a narrow, opaque opening, the same residue often remains invisible and unreachable by a brush, where it grows undisturbed.
Limits of the design
Low maintenance does not mean maintenance-free for us. The ball is not a part for the entire toilet lifetime without inspection: if it becomes stuck due to heavy scaling, it no longer seals reliably, and there is no warning light for this. An independent long-term test over several years is still pending for this part. Therefore, checking its mobility regularly is part of routine maintenance, not just flushing. The exact cleaning routine with dosing and intervals for citric acid, the separating insert, and the solid waste container is shown in Cleaning the separating toilet.
Availability
The disassemblable urine path is standard in every BioTioo 2.0. The SmellX odor trap comes with every BioTioo and is also available separately as a replacement and retrofit part; it also fits many dry and composting toilets with DIN-96 wide-neck canisters. All models are listed in the overview of dry separating toilets. The bowl and lid come with a 3-year warranty plus a 60-day return policy.
