Has your composting toilet started to smell? You shouldn't have to put up with it. Start with airflow, then check moisture, recent use and cleaning—those checks can help you find what's changed.
Persistent odour isn't an unavoidable part of having a composting toilet. Before buying another additive or changing your whole routine, work through the basics below. Make a note of what you find so you can get useful help if the cause isn't obvious.
Find the cause before adding a treatment
Check the required ventilation and any liquid outlet first, then think about changes in use. An additive may help with recovery once you've identified the problem, but it can't restart a failed fan, reconnect a vent or unblock a drain.
The Exhaust Fan Has Stopped Working
If your system needs powered ventilation, check that its supply and fan are working as intended. Listen to the fan, but don't stop there: it can make a noise even if air can't move freely through the rest of the vent.
Inspect the parts you can safely reach: screens, duct connections, seals and the vent outlet. Look for damaged flexible duct, debris or water trapped in a low section. Check that air can enter the room to replace what the toilet extracts, and whether a new bathroom extractor has changed the airflow.
Isolate the power before any cleaning or replacement task allowed by the manual, and refer electrical faults to an appropriately qualified person. Follow the model's instructions about use during a failure. A wind-driven cowl isn't automatically an adequate substitute for the required fan.
The Compost Pile Is Too Wet
A waterlogged pile has less space for air. First work out why the liquid is building up: has the toilet had more use, is the mix too compact, is the drain blocked, or has ventilation dropped? The receiving system or installation may need checking too.
- Has the toilet had more regular users or a recent run of visitors than it was selected for?
- Is the drain, where fitted, and the system receiving its liquid working properly? Keep any discharge contained during checks.
- Are you adding the correct bulking material at the recommended rate?
- Is ventilation working, and are you following the specified mixing or levelling routine?
- If the material has flooded, been contaminated or moved well outside normal conditions, ask for a recovery plan for your model.
We may recommend a targeted product, such as Compost Black™ biochar, as part of recovery. Match the product and quantity to the problem. Correcting a blocked drain or failed vent comes before repeatedly adding more material.
Cleaning Products Have Disrupted the Process
Have you recently changed cleaners, used a disinfectant or drain treatment, or accidentally put a chemical into the toilet? Keep the label and note roughly how much went in. That information is more useful than assuming the whole compost pile has been killed.
Stop using the suspected product and contact us with its label or safety data sheet. Don't try mixing chemicals or pouring in concentrated treatments to cancel it out. Biological additives cannot be relied on to remove chemical contamination or make hazardous residues safe.
For normal cleaning, use products accepted for your system at the specified dilution. If there has been a contamination incident, get advice for that incident rather than treating it as routine cleaning.
The Compost Has Dried Out
Has the property been empty for a while? Have you added more dry cover material than usual? Those changes, along with unsuitable operating conditions, can leave the compost too dry. The organisms need moisture as well as oxygen.
Check your manual before adding water. If moisture needs correcting, use the controlled amount and method specified for the model. A dry collection toilet may be designed to keep its contents differently from an active composting chamber.
Review the bulking dose, airflow and any heating settings that the user instructions allow you to check. Make the recommended adjustment rather than adding a large volume of liquid and creating a wet pile instead.
Check the Smaller Details Too
The compost may not be the source. Check the urine-container cap, seals, bowl, hoses and any residue outside the chamber. Clean and inspect accessible parts using your model's instructions.
Notice when and where the smell appears. Is it constant, after heavy use, only when another extractor runs, or outside near the vent? Those details help us distinguish a care issue from an installation or airflow problem.
Once you've found and corrected the cause, return to the recommended routine. That gives the composting process a chance to work without a succession of unplanned changes.
Still not sure where the smell is coming from?
Call WCTNZ® on 0800 022 027. Tell us your model, when the smell started and which checks you've made. We can help you decide what to look at next.
