A urine diverter is a separator at the front of the toilet seat that sends urine forward into its own container and lets solids fall backward into the compost, which keeps the solids drier and removes roughly 85-92% of the volume from the compost. Dilute collected urine 1:10 with water before use, apply it at the base of plants and not on leaves, and never send it to the compost chamber or the greywater system.
Part of Composting Toilet Systems
Urine diversion splits human waste at the seat into a liquid stream, urine, and a solid stream, faeces. Urine is high in nitrogen, phosphorus and potassium and can be used as a liquid fertiliser; the solids compost more easily without it.
Why Dividing The Two Streams Pays Off
- Volume. Using recalled published figures (about 1.4 L of urine against 0.13-0.25 L of faeces per person per day, not re-read), urine is 1.4 ÷ (1.4 + 0.25) = 85% to 1.4 ÷ (1.4 + 0.13) = 92% of the total. The first-month page puts it at about 90%.
- Moisture. Urine in the compost makes it wet and airless, slow to heat and smelly. Chamber Sizing shows that for four people undiverted urine multiplies the chamber volume needed from 1.15-1.83 m³ to 3.7-4.4 m³.
- Nitrogen. Urine is about 0.8:1 carbon to nitrogen according to Composting Basics, so it skews the compost ratio (Carbon-to-Nitrogen Ratio).
- Resource. It gives an immediate garden fertiliser, comparable in nitrogen, phosphorus and potassium to commercial fertiliser, as the parent page says.
What You Need
- A diverter — molded or carved; the first-month page lists a split coconut shell, a carved wooden divider or an angled clay insert as improvised forms
- A short, steep, wide pipe from the diverter to the container
- A sealable container outside the vault, labelled as urine
- A small water seal or trap in the pipe to stop smell rising (a U-bend with a little water)
- Clean water for rinsing the diverter and pipe
Method: Build And Use
Step 1: Shape the front of the seat. The diverter sits at the front of the seat opening. Urine strikes the front surface and runs forward into the pipe; solids drop past the back edge into the compost chamber or bucket.
Step 2: Pipe it out. Run the pipe straight and steeply downward, without sags where liquid could pool. Keep it short.
Step 3: Collect in a sealed container. Fit a lid so that ammonia does not escape and flies cannot enter.
Step 4: Rinse. Rinse the diverter and pipe with a small amount of clean water; crystals of salts slowly build up in urine pipes and narrow them, as I recall, so wide bore and regular rinsing prevent blockages.
Step 5: Dilute and apply. Mix 1 part urine with 10 parts water. Apply at the base of plants, not on leaves, and in the evening to reduce ammonia loss. Undiluted urine burns plants (parent page).
Worked Example: A Family Of Four
- Urine = 4 × 1.42 L = 5.7 L per day (recalled figure).
- Diluted 1:10, one part urine plus ten parts water = 11 parts: 5.7 × 11 = 62 L of ready solution per day.
- Over a year: 5.7 × 365 = 2,070 L of undiluted urine.
That is a lot of liquid for a small garden. Use it year-round only if the soil can take it; excess nitrogen burns plants and salts accumulate.
Hygiene: “Essentially Sterile” Is Not “Guaranteed Clean”
The parent page calls urine essentially sterile. It leaves the body almost germ-free, but a seat and pipe also catch faecal matter, so collected urine can carry faecal organisms. Keep it off leaves and edible parts, apply it to the soil, wash hands after handling, and stop applying it well before harvest. The first-month page says to wait 24 hours before harvest; I treat that as the least acceptable and have no sourced storage period to recommend, so for crops eaten raw leave much longer or use only on ornamentals and trees.
Common Mistakes
- A long, flat pipe. Liquid pools, scales and smells.
- Pouring urine on leaves or undiluted. Burns the plant and risks contact with edible parts.
- Piping it into greywater or the compost chamber. It defeats both systems.
- Storing it unsealed. Ammonia loss and smell.
Safety
Never mix urine with bleach or acid cleaners
Urine contains ammonia compounds; bleach mixed with them releases toxic chloramine gas, and acids can release other toxic gases. Rinse the diverter with plain water. Keep the container sealed, labelled and out of reach of children. Wash hands with soap or ash and water after any contact.
What’s Next
- Learn next: Safe Application in Gardens — how to apply urine and compost safely
- Combine with: Dual-Chamber (Batch) Design — drier chambers fill slower