8 Essential Diy Urine Diverter Parts For Tiny Home Bathrooms

Step into a tiny house or custom van conversion, and the first question most visitors ask is how the bathroom situation works. Building a DIY urine-diverting toilet is the ultimate hack to bypass expensive commercial systems while completely eliminating off-grid bathroom odors. Success depends on selecting robust, durable components that prevent leaks, stop smells, and withstand years of daily use.

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Why Build a DIY Urine Diverting Toilet System

Standard flush toilets waste thousands of gallons of clean water, while traditional blackwater holding tanks turn tiny spaces into toxic-smelling waiting games. A urine-diverting toilet solves this by separating liquid from solid waste immediately. When mixed, these two elements create anaerobic rot, which produces the notorious sewage smell. Keeping them apart keeps your bathroom completely odor-free.

Commercial composting toilets are excellent, but they often carry price tags near a thousand dollars. A DIY build allows you to customize the toilet box footprint to match the exact dimensions of a micro-bathroom. You also gain complete access to every part, making troubleshooting and deep cleaning incredibly simple.

Building your own setup also means choosing the exact materials that match your aesthetic. You are not locked into a bulky, clinical-looking plastic unit. A well-designed DIY wooden box can blend seamlessly into your tiny home’s design while functioning just as efficiently as a commercial model.

Urine Diverter – Kildwick Separator Klassik

The urine diverter is the absolute heart of your DIY toilet system. Its sole job is to capture liquid waste at the front and route it away while letting solid waste fall cleanly into a separate rear container. If this component fails or fits poorly, the separation process collapses, leading to immediate odor issues.

The Kildwick Separator Klassik is the gold standard for this task because of its deep, ergonomically optimized bowl. Crafted from high-gloss, impact-resistant ABS plastic, this diverter is incredibly tough and resists staining or scratching over years of use. Its wide rim allows for easy mounting beneath your toilet box top, creating a seamless, sanitary barrier.

• Material: 4mm thick recyclable ABS plastic
• Dimensions: 395mm x 340mm (approx. 15.5″ x 13.4″)
• Spigot outer diameter: 32mm (fits standard 1.25″ hoses)
• Finish: High-gloss white for easy cleaning

When installing this diverter, ensure it sits flush against the underside of your toilet bench to prevent any fluids from seeping into the wooden structure. Regular wiping with a simple water-and-vinegar spray keeps the surface pristine without damaging the plastic.

This diverter is perfect for builders who want a dependable, easy-to-clean interface that fits standard toilet seat footprints. It is not suitable for ultra-compact micro-toilets where space is too tight to accommodate its full dimensions.

Drain Hose – Shields Vac Extra Heavy Duty Hose

The drain hose connects your urine diverter to either an internal collection bottle or an external greywater system. Standard corrugated bilge hoses might seem like an easy, cheap choice, but they have a fatal flaw. Their interior ridges trap urine droplets, which quickly crystallize, restrict flow, and release terrible odors.

The Shields Vac Extra Heavy Duty Hose solves this problem with its smooth internal bore. This smooth interior prevents liquid from pooling and stops urine scale from building up along the walls. It is constructed from heavy-duty PVC and reinforced with a rigid helix, making it incredibly resistant to kinks and collapses.

• Inside Diameter: 1.5 inches (standard sizing)
• Material: Odor-permeation resistant PVC
• Construction: Smooth interior wall with rigid vinyl helix
• Application: Sanitation lines, holding tank connections

Keep in mind that this hose is highly rigid to prevent odors from leaking through the plastic walls. This means it has a wider bend radius, so you must plan your plumbing runs with gentle curves rather than sharp 90-degree turns.

This hose is ideal for long-term dwellers who want to eliminate plumbing-related odors permanently. It is not ideal for builders working in extremely tight, cramped boxes that require tight, sharp bends.

Urine Container – Kildwick 10L Spigot Bottle

If your tiny home isn’t plumbed directly into an external greywater system, you need a reliable vessel to catch liquid waste inside the toilet box. This container must be easy to remove, completely leak-proof, and sized appropriately for easy transport. A bottle that is too large becomes incredibly heavy and difficult to dump.

The Kildwick 10L Spigot Bottle strikes the perfect balance between capacity and portability. Ten liters of liquid weighs roughly 22 pounds, which is a manageable weight for almost any user to carry. The bottle features a wide, integrated handle and a sturdy design that prevents it from tipping over inside your toilet box.

• Capacity: 10 Liters (2.6 Gallons)
• Material: Heavy-duty, UV-stabilized HDPE
• Opening: Wide mouth for easy cleaning and hose insertion
• Form Factor: Compact, slim profile for space saving

Make sure to empty the container every few days, even if it is not completely full. Leaving urine sitting for too long allows bacteria to multiply, which leads to ammonia odors.

This bottle is perfect for single occupants or couples who want a clean, manageable way to handle liquid disposal. It is not necessary for those plumbing their liquid drain directly into an external greywater holding tank or French drain.

Solids Bin – Leaktite 5-Gallon Plastic Bucket

The solids bin sits directly beneath the rear opening of your diverter to collect dry waste and bulking material. It needs to be tough, chemical-resistant, and cheap enough to replace easily if needed. It also must match standard toilet box dimensions to keep your seating height comfortable.

The Leaktite 5-Gallon Plastic Bucket is a simple, highly effective solution that costs very little. Its dimensions match standard residential toilet heights perfectly when housed inside a custom box. Made from high-density polyethylene (HDPE), this bucket is incredibly strong and will not degrade under the influence of moisture or waste.

• Capacity: 5 Gallons (approx. 19 Liters)
• Material: Heavy-duty, BPA-free HDPE plastic
• Handle: Metal wire with plastic grip for easy carrying
• Compatibility: Fits standard 12-inch toilet box heights

Always line this bucket with a high-quality compostable liner bag before use. This keeps the bucket itself clean and makes emptying the solids a quick, sanitary process.

This bucket is perfect for anyone building a standard, cost-effective composting toilet. It is not the right choice for ultra-shallow or low-profile toilet builds that require a custom-shaped or shorter container.

Ventilation Fan – Noctua NF-A12x25 PWM 12V

A reliable ventilation fan is the secret to a completely odorless composting toilet. Its job is to run continuously, drawing air into the toilet box and pushing it outside. This constant negative pressure prevents odors from escaping into your tiny home bathroom.

The Noctua NF-A12x25 PWM 12V fan is a legendary choice among off-grid builders because it is nearly silent. It draws incredibly little power—often less than two watts—which is crucial for off-grid solar setups. Its SSO2 bearing system ensures it can run 24/7 for years without wearing out or getting loud.

• Dimensions: 120mm x 120mm x 25mm
• Power Input: 12V DC (perfect for off-grid battery systems)
• Acoustical Noise: Extremely low 22.6 dB(A)
• Lifespan: Over 150,000 hours of continuous operation

To keep the fan running efficiently, install a fine mesh screen before the vent line to prevent dust and bugs from building up on the blades. You will also need to wire this into your tiny home’s 12V DC electrical system.

This fan is the ultimate choice for full-time tiny home dwellers who prioritize silent operation and low power draw. It is not suitable for those without a constant 12V DC power source.

Vent Hose – AC Infinity Flexible Ducting

Your ventilation fan needs a clear, sealed pathway to push humid, smelly air out of the toilet box and through your tiny home’s exterior wall. A cheap, thin duct will tear easily, allowing damp, smelly air to leak into your wall cavities. You need a durable duct that can navigate the tight spaces behind your toilet box.

The AC Infinity Flexible Ducting stands out due to its dual-layer construction. It features an aluminum inner layer paired with an outer thermoplastic wall, making it highly resistant to tears and punctures. It is flexible enough to bend around tight framing members without restricting airflow.

• Diameter Options: 3 inches or 4 inches (3″ is ideal for tiny homes)
• Material: Dual-layer aluminum and PVC
• Accessories: Includes heavy-duty screw clamps
• Length: Highly compressible and expandable up to 8 feet

When routing this ducting, keep the run as straight as possible to maximize airflow. Any sharp kinks or sagging loops can trap condensation, which will eventually block the flow of air.

This ducting is perfect for builders who want a robust, tear-proof pathway for their toilet ventilation system. It is not necessary if your toilet box sits directly against an exterior wall and vents straight out the back without routing.

Toilet Seat – Bemis 1500EC Wood Toilet Seat

The toilet seat is your primary physical interface with the toilet, and it plays a major role in the overall feel of your bathroom. Flimsy plastic camper seats flex, squeak, and feel cheap. A solid, residential-grade toilet seat makes your DIY build feel like a high-end, permanent fixture.

The Bemis 1500EC Wood Toilet Seat features an enameled wood construction that provides a solid, premium feel. Its Easy Clean & Change hinges allow you to lift the seat completely off the toilet box with a simple twist. This makes cleaning the urine diverter and the box rim incredibly easy.

• Material: Molded wood with high-gloss enamel finish
• Hinge System: Twist-to-unlock plastic hinges
• Shape: Round (fits standard DIY box dimensions)
• Hardware: Corrosion-free top-tite bolts

Because this seat is made of wood, it is heavier than plastic alternatives. Ensure your DIY toilet box lid is sturdy enough and has strong hinges to support the weight when lifted.

This seat is ideal for those who want their tiny home bathroom to feel like a high-end residential space. It is not suitable for mobile setups where saving every single ounce of weight is critical.

Bulking Agent – Coco Tek Organic Coir Pith

Every time you use the solids side of your toilet, you must cover the waste with a dry bulking agent. This material absorbs moisture, prevents insect access, and jumpstarts the aerobic composting process. Using the wrong material, like heavy soil or non-absorbent wood chips, leads to bad smells and slow decomposition.

The Coco Tek Organic Coir Pith is highly recommended because of its incredible absorption capacity. Made from coconut husks, it is a sustainable, organic material that expands rapidly when prepared. It is naturally odor-absorbent and has a fine texture that covers solids completely with very little volume.

• Material: 100% organic coconut coir pith
• Form Factor: Highly compressed, lightweight block
• Absorption: Retains up to nine times its dry weight in water
• Yield: One block expands to create a large volume of loose material

To use coir pith, you must first hydrate the block with a small amount of water to expand it, then let it dry until it is barely damp. Storing it in a sealed bucket next to your toilet keeps it dry and ready for use.

This bulking agent is perfect for off-grid dwellers looking for highly effective, natural odor suppression. It is not ideal for those who prefer a ready-to-use option that requires zero preparation or hydration.

How to Vent Your DIY Toilet for Zero Odor

The key to a completely odorless composting toilet is maintaining constant negative pressure inside the toilet box. This means air should only flow into the toilet seat opening and out through your vent hose. To achieve this, seal all seams of your wooden toilet box with silicone caulk during assembly.

Position your 12V fan so it pulls air out of the box and pushes it into the vent hose. Vent the air to the exterior of your tiny home, ideally high up on a wall away from windows or outdoor seating areas. Installing a simple louvered vent cover on the outside protects your home from wind and rain.

Keep the fan running continuously, 24 hours a day. The constant airflow not only carries odors away but also dries out the solids bin. Moisture is the enemy of odor control, so drying out the waste is your best defense against bad smells.

Sizing and Plumbing Your Liquids Drain System

If you choose to drain your liquid waste directly to an external greywater system rather than an internal bottle, planning is critical. Urine contains minerals that can precipitate out and form a hard crust called urine scale. To prevent this, always design your drain line with a steep slope of at least one-quarter inch per foot.

Keep the plumbing run as short and direct as possible. Avoid loop traps or standard P-traps in your urine line, as standing urine in a trap will quickly smell and clog with scale. Instead, use a waterless trap, like a HepvO valve, which allows liquid to flow through but blocks gases from rising back up.

If you are plumbing into an external greywater tank, ensure the tank is properly vented. A closed tank can create backpressure, slow down your drain rate, and cause backup issues at your toilet’s diverter.

Essential Maintenance Tips for Off-Grid Toilets

Operating a DIY urine-diverting toilet requires a shift in your daily bathroom habits. Keep a spray bottle filled with a mix of water and white vinegar next to the toilet. Spray the urine diverter clean after every use to prevent scale buildup and eliminate lingering drops.

Never use harsh chemical cleaners, bleach, or antibacterial sprays on the solids bin or the diverter. These chemicals will destroy the beneficial bacteria needed to break down the solids and will quickly ruin the plastic components. Stick to natural, bio-compatible cleaners that support the composting process.

Finally, monitor your solids bin level carefully and empty it before it fills to the brim. A regular schedule—typically every two to three weeks for two people—makes the task manageable and sanitary. Always dispose of your composted waste in accordance with local regulations.

Conclusion

Building your own urine-diverting toilet is a highly rewarding project that delivers true off-grid independence. By selecting high-quality components like a solid diverter, heavy-duty hoses, and a silent fan, you ensure your tiny home bathroom remains clean, fresh, and functional. With a little planning and regular upkeep, your custom setup will rival any commercial unit on the market.