Conversion Kit Transforms Conventional Toilets Into Dual-Stream Waste Separation Systems

Conventional combined-waste toilets create disposal challenges by mixing solid and liquid waste, increasing treatment complexity and environmental burden. Many municipalities now prefer waste separation at the source to enable solids recovery and liquid processing optimization. This innovation adds separation capability to existing toilets through a retrofit kit featuring separate valve arrangements that direct solid and liquid waste into distinct collection systems while maintaining familiar user interfaces.

The Problem

Modern sanitation challenges extend beyond basic waste handling. Wastewater treatment plants increasingly prefer separated waste streams: solid waste can be composted or processed separately, while liquid waste undergoes biological treatment. Current combined-waste toilets force costly downstream separation processes. Nutrient recovery, energy production, and agricultural applications all depend on preventing mixing of waste streams that should remain separate.

Retrofitting existing toilet infrastructure to achieve separation poses challenges. Most installed toilets use combined designs that cannot be modified. Full replacement requires expensive construction work, plumbing modification, and temporary loss of facilities. Renters and people with temporary facilities face practical barriers to upgrading. Developing regions implementing new sanitation infrastructure would benefit from affordable separation technology that works with existing building plumbing.

What This Invention Does

The apparatus enables conversion of a combined-waste toilet into a separation toilet by modifying the toilet bowl to include separate openings for solid and liquid waste. A solid waste valve mounts over the solid waste opening, remaining closed during liquid waste elimination and opening to allow solid waste passage. When closed, the valve prevents liquid waste from entering the solid waste stream.

Solid waste drops through its dedicated opening into a removable bin positioned below the toilet bowl. Liquid waste flows through a separate opening connected to a liquid waste tank or system disposed below the bowl level. Valve arrangements in communication with the liquid waste opening control flow from the toilet to the storage or treatment system.

A solid waste valve in the open position receives solid waste from the bowl. The prepositioned waste valve arrangement remains in the closed position to block liquid flow into the solid waste system. When the user switches to liquid waste elimination, the arrangement reverses: the solid valve closes while liquid flow to the dedicated tank enables. A stabilizing device fixed to the packaging assists with proper valve positioning during installation.

Key Features

• Dual Opening Bowl Design. The modified bowl includes separate openings for solid and liquid waste, positioned to achieve natural separation without requiring user actions beyond conventional toilet use.
• Solid Waste Valve. A dedicated valve over the solid opening switches between open and closed states. Open position permits solid waste entry; closed position prevents liquid contamination.
• Liquid Waste Valve Arrangement. A second valve system controls liquid waste flow to the collection tank. It remains closed during solid waste elimination.
• Removable Solid Waste Bin. The solid collection container sits directly under the bowl opening, catching separated waste in a contained receptacle for transport or composting.
• Below-Bowl Liquid Tank. The liquid waste system installs at an elevation lower than the bowl, allowing gravity-assisted flow without requiring elevated water pumps or pressure systems.
• Kit Format Design. The apparatus arrives as a conversion kit that adapts existing toilets without requiring full bowl replacement or major plumbing modification.
• Stabilizing Device. A supporting framework ensures proper valve positioning and alignment of solid and liquid waste openings for reliable separation.
• Natural Elimination Process. Users operate the toilet normally; the separation mechanism responds automatically to waste type without requiring conscious selection or adjustment.

Who Is Behind It?

Thetford BV, a Dutch company specializing in sanitation technology for recreational vehicles, boats, and stationary installations, developed this separation toilet conversion system. Multiple inventors contributed to the design: Jacco Van Beek, Dennis Doove, Tom Kieboom, Leendert Jan Antoon Jansen, Harm De Rooij, and Victor Luijk. The application claims priority from a U.S. design patent filed 28 August 2024. Henry Hughes IP Ltd in Wellington provides representation.

Why It Matters

Sanitation infrastructure across developing regions faces pressure to handle waste sustainably. Waste separation at the toilet source enables downstream composting, nutrient recovery, and energy production that combined systems cannot achieve. This retrofit approach makes separation technology accessible to users of existing facilities without requiring full plumbing system overhauls.

Environmental benefits extend beyond treatment efficiency. Separated solid waste can improve agricultural soils through composting. Liquid waste treatment becomes simpler and more efficient. Nutrient recovery becomes possible, reducing dependency on synthetic fertilizers. For small communities, institutions, and temporary facilities, this conversion approach offers a practical path toward sustainable sanitation without capital-intensive infrastructure replacement.

Related Concepts

A urine-diverting dry toilet separates liquid and solid waste at the point of use, dramatically simplifying downstream treatment. Combined with ecological sanitation principles, separated waste can be safely composted or used as agricultural nutrients rather than requiring energy-intensive treatment.

Wastewater treatment costs and complexity increase significantly when solid and liquid waste streams are mixed. Source separation – diverting streams before they mix – is increasingly recognised as a sustainable sanitation strategy that reduces infrastructure burden and enables nutrient recovery.

---

AU 2025217364 was published in the Australian Official Journal of Patents on 19 March 2026 and is open for public inspection. Patent applications represent inventions that are sought to be protected and do not necessarily reflect commercially available products.