9 Essential DIY Composting Toilet Supplies and Urine Diverters for Off-Grid Living

Stepping off the grid doesn’t mean sacrificing basic sanitation, but relying on a standard black water tank can quickly tether you to RV dump stations. Building a DIY composting toilet is the ultimate way to reclaim your independence while saving water, money, and valuable cabin space. With the right selection of diverters, ventilation components, and processing substrates, you can construct a system that is entirely odorless, highly efficient, and incredibly easy to maintain.

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Designing a Reliable DIY Off-Grid Toilet

The gold standard of off-grid sanitation relies on one simple rule: keep the liquids separate from the solids. When urine and feces mix, they create anaerobic conditions that produce the dreaded sewage smell most people associate with outhouses. By isolating the two waste streams, the solids dry out quickly while the liquids can be diverted to a dedicated greywater system or a portable storage jug.

Designing your own toilet box allows you to customize the dimensions to fit your specific layout, whether that is a tight van corner, an RV wet bath, or a spacious tiny house bathroom. The frame is typically built out of sturdy plywood, sealed with polyurethane to resist moisture, and fitted with a hinged lid for easy access to the internal containers.

A successful build requires careful planning around ergonomics and maintenance. You must ensure the height is comfortable for daily use while leaving enough clearance underneath to easily slide out the waste buckets without spilling. Integrating passive or active ventilation is also critical, as it continuously pulls moisture away from the solids pile to accelerate dehydration.

Urine Diverter – Separett Privy 501 Diverter

A high-quality urine diverter is the most critical component of any DIY composting toilet system. It sits at the top of your toilet box and ensures that liquids flow forward into a collection jug while solids drop straight down into a bucket. Without a reliable diverter, the separation process fails, leading to instant odor issues and messy cleanup.

The Separett Privy 501 is a gold standard molded-plastic diverter that easily retrofits into homemade wooden toilet boxes. It features a wide, deep urine bowl that prevents splashing and misdirection, along with a comfortable foam seat insert that provides warmth in cold climates. The high-impact polystyrene plastic is non-porous and remarkably easy to wipe down.

• Material: High-impact polystyrene (highly durable and UV-resistant)
• Dimensions: Approximately 18.5″ x 14.7″ x 6.7″
• Hose Connection: Includes a 3.2-foot flexible drain hose (approx. 1.25″ diameter)
• Included Accessories: Insulation seat for thermal comfort

Installation requires cutting a precise template out of your toilet box’s top deck. Because it comes with a built-in toilet seat, you cannot easily swap it out for a heavy-duty household wooden seat. The provided drain hose must be routed downward with a continuous slope to prevent standing urine and subsequent crystal buildup inside the pipe.

This diverter is perfect for DIYers who want an all-in-one seat and separation solution that is lightweight and highly functional. It is not ideal for those who prefer the look and feel of a heavy, traditional domestic toilet seat, or for ultra-compact builds where every fraction of an inch of height must be minimized.

Toilet Seat – Bemis Round Slow-Close Wood Seat

For those who build a custom wooden toilet box and mount their diverter beneath the top deck, a traditional toilet seat is required. The seat acts as both the user interface and the primary physical barrier that seals the toilet box when not in use. A flimsy seat will flex and leak air, allowing odors to escape into your living space.

The Bemis Round Slow-Close Wood Seat brings domestic comfort to a rustic off-grid setup. Unlike cheap plastic seats that bend and flex, this enameled wood seat offers a solid, premium feel that makes your DIY toilet feel like home. Its slow-close hinges prevent accidental slamming, which is a major nuisance in quiet, small-space living environments like vans or tiny homes.

• Material: Durable enameled wood with a high-gloss finish
• Hinge System: STA-TITE Fastening System to prevent loosening
• Closure: Whisper-Close hinge mechanism
• Compatibility: Fits standard round toilet bowls and DIY platforms

Because wood is heavier than plastic, ensure your toilet box hinges and top lid are robust enough to support the weight. The high-gloss enamel coating makes it easy to clean, but harsh abrasive cleaners should be avoided to prevent stripping the protective sealant. This seat works best when paired with DIY systems where the diverter is mounted directly flush with the underside of the wooden lid.

This is the ultimate choice for off-grid builders aiming to replicate a residential bathroom experience. It is not suitable for ultra-lightweight mobile builds where every ounce of payload matters, or for wet bath installations where the seat will be directly exposed to shower water.

Liquid Jug – Reliance Products Aqua-Tainer 4G

Reliance Products Aqua Tainer 7 Gallon Drinking Water Storage Container Tank (4 Pack)

The liquid collection container sits directly beneath the urine diverter outlet to store liquid waste safely. It must be leak-proof, easy to carry, and sized appropriately to handle several days of usage without overflowing. A poor container choice can result in spills during transport or offensive odors permeating through the plastic walls.

The Reliance Products Aqua-Tainer 4-Gallon rigid container is a favorite among off-grid builders due to its space-saving cubic shape and robust construction. Unlike standard round jugs, the square profile maximizes every inch of space inside a toilet cabinet. Its thick, food-grade polyethylene wall prevents chemical odors from leaching through the plastic.

• Capacity: 4 Gallons (approx. 15 Liters)
• Shape: Space-efficient cubic design
• Material: BPA-free, heavy-duty polyethylene
• Cap Style: Screw-on cap with an integrated hideaway spigot

A 4-gallon container filled with liquid weighs roughly 33 pounds, making it manageable to carry to a disposal site but heavy enough to require a sturdy handle. You will need to drill a hole in the cap to feed your diverter’s drain hose into the container. It is vital to leave a small air gap around the hose entry to prevent air-locking, which would stop the urine from draining freely.

This container is perfect for solo off-grid dwellers or couples who want a reliable, leak-proof storage system that lasts 3 to 5 days before needing to be emptied. It is not the right choice for large families who will quickly overwhelm a 4-gallon capacity, or for setups where vertical space inside the toilet box is strictly limited.

Solids Bucket – Hudson Exchange 5 Gallon Bucket

The solids bucket is the collection point for human waste and carbon cover material. It must be rugged, chemically resistant, and easy to clean. Because this bucket is lined and emptied regularly, the internal dimensions and rim style must accommodate standard compostable trash liners without tearing them.

The Hudson Exchange 5 Gallon Bucket is a commercial-grade, heavy-duty HDPE bucket that is incredibly resistant to cracking and chemical degradation. Its uniform cylindrical wall ensures that compostable liners hang evenly without snagging on rough plastic edges. The sturdy metal bail handle with a plastic grip makes lifting and transporting a full bucket safe and secure.

• Capacity: 5 Gallons (approx. 19 Liters)
• Material: High-density polyethylene (HDPE), 90 mil thickness
• Handle: Heavy-duty steel wire bail with plastic handle grip
• Safety: Food-grade certified (helps guarantee no chemical off-gassing)

Standard 5-gallon buckets stand about 14.5 inches tall, which dictates the minimum height of your toilet box build once you factor in the seat thickness and clearance. Always verify that your bucket can be easily slid out from either the top or a front-facing door of your toilet cabinet. It is wise to have a spare bucket on hand with a tight-fitting lid in case you cannot dump your waste immediately.

This is the standard, reliable core for 95% of DIY composting toilets, offering cheap, indestructible performance. It is not suitable for ultra-compact builds (like low-profile slide-out drawers in van conversions) which may require a shallower 2-gallon or 3-gallon bucket instead.

Exhaust Fan – Noctua NF-A8 FLX Premium Fan

Active ventilation is the difference between a toilet that smells and one that doesn’t. A small exhaust fan runs continuously to pull moisture out of the solids bin and vent it outside, which dries out the waste and prevents odor from entering the living area. The fan must be energy-efficient, highly durable, and extremely quiet.

The Noctua NF-A8 FLX is legendary in the computer building and off-grid worlds for its whisper-quiet operation and extremely low power draw. Running 24/7, this 80mm fan consumes minimal wattage, making it ideal for solar-powered 12V electrical systems. Its proprietary SSO2 bearing ensures years of continuous, maintenance-free operation in humid environments.

• Dimensions: 80mm x 80mm x 25mm
• Voltage: 12V DC (perfect for off-grid battery banks)
• Noise Level: Ultra-low 16.1 dB(A) at full speed
• Airflow: 31.1 CFM (Cubic Feet per Minute)

To wire this fan directly into a 12V DC fuse block, you will need to splice its 3-pin connector. It is highly recommended to mount the fan inside a dedicated shroud that transitions cleanly to your vent hose. Ensure you clean the fan blades once or twice a year, as fine dust from the composting cover material can accumulate and degrade performance over time.

This fan is a must-have for tiny houses, vans, and RVs where even the slightest fan whine is a distraction in a small space. It is not suitable for heavy-duty commercial installations that require massive airflow to clear large, unmanaged volumes of wet waste.

Vent Hose – SeaDog Line Flexible Bilge Hose

A vent hose carries the moisture-laden, warm air from your toilet box to the exterior of your shelter or vehicle. It must be flexible enough to navigate tight routing pathways but tough enough to resist crushing, UV exposure, and the corrosive nature of sewer gases.

The SeaDog Line Flexible Bilge Hose is designed to withstand harsh marine environments, making it incredibly resilient against moisture, acidic fumes, and physical wear. Its corrugated design allows for tight bends without collapsing, which is critical when routing ducting through cramped cabinets. The smooth interior walls minimize airflow resistance and prevent condensation traps.

• Material: High-quality, chemical-resistant polyethylene
• Diameter: 1.5 inches (the perfect size for low-CFM 12V fans)
• Flexibility: Non-kinking construction
• End-Cuffs: Molded cuffs every foot for secure hose clamp attachment

When installing the hose, route it with as few sharp 90-degree turns as possible to maintain optimal airflow. Any downward dips in the line can collect condensation, which can eventually block airflow and lead to mold growth. Use high-quality marine-grade stainless steel hose clamps to secure the hose ends to the fan shroud and the exterior vent cap.

Excellent for builders routing ventilation through complex, tight pathways in mobile rigs. It is not suitable for long vertical runs in stationary cabins, where rigid PVC pipe is a more durable and permanent choice.

Coconut Coir – Coco Tek Organic Coir Brick

Coco Coir 650gm Bricks (5-Pack) - Organic Coco Coir for Plants & Gardening - OMRI-Listed Cocopeat for Garden Soil, Seed Starter Soil, & Mulch - Organic Coconut Bricks - Coconut Fiber Potting M...

Every composting toilet requires a carbon-rich cover material to toss over solids after each use. This material absorbs moisture, prevents insect breeding, and introduces the carbon needed for composting to begin. Without a proper cover material, the solids bucket will remain wet, anaerobic, and highly offensive.

Coco Tek Organic Coir Bricks provide an exceptional carbon medium that expands rapidly when hydrated, offering a highly absorbent and fibrous substrate. Unlike wood shavings, which can contain irritating dust and aromatic oils that slow down composting, coconut coir is completely organic, pH-neutral, and highly effective at trapping odors. Its natural structure allows oxygen to circulate, promoting aerobic decomposition.

• Form Factor: Compact, compressed brick (easy to store in small spaces)
• Yield: Expands to roughly 2 to 2.5 gallons of loose material per brick
• Material: 100% natural, organic coconut fiber (coir)
• Water Retention: High moisture absorption capacity

You must hydrate the brick in a separate bucket before use; it should feel like damp, wrung-out sponge—not soaking wet. If you prep too much at once, keep the storage container sealed to prevent it from drying out completely. Adding too much water during preparation can introduce excess humidity to your toilet box, triggering odors and fruit flies.

Essential for off-grid dwellers looking for a compact, highly absorbent cover material that is easy to store in a van or RV. It is not ideal for those who want a dry, ready-to-use-out-of-the-bag cover material without the hassle of hydration, in which case peat moss or fine sawdust is preferred.

Compostable Liners – UNNI 100% Compostable Bags

Compostable liners make emptying your solids bucket a quick, clean, and hygienic process. Rather than scrubbing out a raw bucket of waste, you simply lift the bag out and dispose of it. The liners must be strong enough to hold heavy organic waste without breaking, yet truly compostable so they break down naturally in a compost pile.

UNNI 100% Compostable Bags are fully certified to biodegrade quickly and safely in back-yard compost systems. Unlike standard plastic bags that never degrade, or cheap “biodegradable” bags that simply break down into microplastics, these plant-starch bags fully integrate into the soil structure. They feature high tensile strength, reducing the risk of a catastrophic tear during bucket removal.

• Capacity: 8 Gallons (ideal fit for standard 5-gallon buckets)
• Thickness: 0.85 Mil heavy-duty rating
• Certifications: US BPI and European OK Compost Home certified
• Material: Plant starch-based resins (no plastic)

Because these bags are designed to break down in the presence of moisture and heat, they have a shelf life and will begin to weaken if left in the solids bucket for more than a week. It is best practice to double-bag the solids bucket if you plan to leave the waste sitting for longer periods. Store unused bags in a cool, dry place to prevent premature degradation.

Perfect for eco-conscious off-grid dwellers who dump their solids into a dedicated composting bin. It is not suitable for those who plan to dispose of their solids directly in trash receptacles (where heavy-duty plastic contractor bags are often legally required to prevent leaks).

Enzyme Cleaner – Biokleen Bac-Out Stain & Odor

Even with perfect technique, urine diverters and jugs will eventually develop a buildup of mineral crystals and organic residue. Traditional chemical cleaners can destroy the beneficial microbes needed for composting and ruin plastic components over time. A specialized biological cleaner is needed to keep the system sanitary.

Biokleen Bac-Out utilizes a unique blend of live enzyme cultures and lime peel extract to digest organic matter rather than simply masking it with synthetic perfumes. It targets urine salts and proteins directly, breaking them down to prevent the formation of smelly ammonia crystals. The formula is completely non-toxic and contains no harsh chemicals, making it safe for plumbing and environment-friendly.

• Active Ingredients: Live enzyme cultures, citrus aurantium dulcis (orange) peel extract
• Application: Spray bottle for targeted cleaning
• Eco-Friendly: 100% biodegradable formula
• Safety: Safe to use around pets, skin, and delicate materials

This cleaner works best when sprayed and left to sit for a few minutes, allowing the enzymes to consume the organic residue. Do not mix it with bleach or other chemical disinfectants, as these will kill the active, beneficial bacteria that do the cleaning work. Keep a small spray bottle of Bac-Out next to the toilet for a quick mist after every use of the urine diverter.

Crucial for anyone managing a urine-diverting toilet who wants to keep smells at bay without resorting to harsh chemicals. It is not necessary for those who have a direct-flush toilet hooked up to a black water holding tank where traditional chemical deodorizers are used.

Key Venting Tactics to Prevent Off-Grid Odor

Perfect ventilation is the secret weapon of any successful DIY composting toilet. The goal is to create a constant negative air pressure system within the toilet box, ensuring that air is drawn down through the toilet seat opening and pushed out through the exterior vent. If your box is properly sealed, no air—and therefore no odor—can escape into your living space.

Focus on minimizing air leaks in your toilet cabinet construction. Use closed-cell foam weather stripping along the underside of the main lid and around the toilet seat base to create an airtight seal when closed. This forces the 12V exhaust fan to draw air solely through the diverter and solids bucket area, concentrating the negative pressure exactly where it is needed most.

Exterior vent cap placement also plays a major role in system performance. Mount the vent cap on the downwind side of your vehicle or cabin to prevent highway winds from forcing air backward through the vent line. Adding a fine mesh bug screen over the exterior outlet is a non-negotiable step to prevent flies, mosquitoes, and wasps from entering your toilet system and breeding.

How to Properly Manage and Empty Your Waste

Managing off-grid waste requires a consistent routine to keep the system hygienic and stress-free. Your liquid jug will fill up much faster than your solids bucket and typically requires emptying every two to three days for two active users. When emptying the liquid container, dump it into a flushing residential toilet, an RV dump station, or a dedicated gravel soak pit, depending on local regulations and environmental guidelines.

Solids management is a much slower process, usually requiring attention every two to three weeks. If you are using compostable liners, lift the bag out of the bucket, tie it securely, and transfer it to a designated compost bin where it can decompose safely over the course of 12 to 18 months. Never use raw, un-composted human waste on edible garden crops, as it can harbor harmful pathogens.

If you are traveling or lack access to a dedicated compost pile, you must dispose of the bagged solids in an approved trash receptacle, similar to how pet waste is managed. Always check local municipal laws regarding landfill disposal of human waste. Keeping a secondary, clean bucket with a sealed lid on hand ensures you can swap containers instantly and manage waste on your own schedule.

Building a custom composting toilet equips your off-grid sanctuary with a highly reliable, waterless sanitation system. By selecting high-quality components and executing a smart ventilation strategy, you eliminate the hassle of traditional plumbing while embracing absolute self-reliance. With your DIY build complete, you are free to explore further and stay out longer without compromise.