Where to start...

There are 4 key considerations when addressing faults with the composting system that need to be inspected. Most composting systems have the following design aspects that are key.

Ventilation systems are used to provide the following

1. Odour free operation
2. Oxygen supply to the composting process
3. Drying or evaporating liquids, keeping in mind that for composting to take place the compost itself must retain appropriate moisture
4. Prevent insects from entering the composting system by providing directional air flow
5. Provide the basic operating conditions the system needs to function as intended

Organic carbon materials

1. Carbon materials feed and support the composting process
2. Provide a bulking bed for waste to break down in
3. Help wick and spread moisture through the composting mass
4. Help the compost remain open, airy, and biologically active
5. Support the production of a more stable end product over time

Human waste load

1. All composting systems have intended use capacities and operating limits
2. Unexpected guest use or sustained overloading can upset moisture balance and slow processing
3. Use patterns, toilet paper use, and climate all influence how the system performs

Climate – temperature & atmospheric conditions

There are a few more considerations to the effectiveness of composting and these include whether the system is heated, the room temperature, airflow conditions, and the local climate. These are addressed further in the manuals and troubleshooting notes below.

Brief Troubleshooting FAQ’s covered here.

See system manuals for comprehensive troubleshooting guides.

Why is the compost chamber filling up too quickly?

This can be caused by an ineffective composting process due to one or more of the issues listed below:

Compost pile being too wet

This means liquid is being trapped in the compost chamber and contributing to quick volume build-up.

For continuous composting systems, check whether moisture is building in the tray or indicator hose and whether the ventilation and heat settings are sufficient for the conditions.

Insufficient air flow

Without sufficient air flow, evaporation slows and odours may begin to escape into the toilet room. A malfunctioning fan, blocked vent, poor room air supply, or badly installed ventilation system can all cause this.

Climate – temperature & atmosphere conditions

WCTNZ® makes every attempt to match you with the right system for your site and climate conditions, but weather patterns and seasonal changes can still create less than ideal situations. In colder climates systems can slow down. In wetter or salt-laden air environments systems may also retain more moisture.

Overuse

Although most systems can tolerate some guest use, unexpected additional users can push the system beyond its practical limit for the site conditions.

Why is the composting process slow to complete?

Composting performance depends on temperature, airflow, moisture balance, and the correct use of bulking material. Listed below are factors that could slow down the process:

Compost pile being too wet

The addition of suitable bulking material is an important part of operating a composting toilet. Bulking material assists with moisture absorption, supports the carbon/nitrogen balance, and helps air move more freely through the composting mass.

Compost pile surrounding temperature is too low

In colder conditions, heated models may require higher operating settings and greater care with ventilation layout and insulation. Low room temperatures can slow microbial activity and reduce the rate of evaporation.

How to deal with insects attracted to the compost pile?

Insects usually indicate that airflow, moisture balance, or cover material routine needs attention. Check that the system is venting correctly, keep fresh bulking material over exposed solids, and review the compost condition.

EcoLet™ - Troubleshooting

The following guide is available in full form in the official EcoLet™ owner’s manuals. These notes are intended as a practical reference for the EcoLet™ 25a, 65a, Separera Mini UD-C, and Separera Mini UD-S systems currently supported by WCTNZ®.

For your convenience, key points are outlined here. To access your model-specific manual, please refer to the corresponding product page or your customer account documents.

Odour present in the toilet room

A properly functioning EcoLet™ system should not produce persistent odour in the toilet room. If odour is present, airflow is usually the first thing to check.

Recommended course of action.

Check that the unit is plugged in, there is power to the plug, and the fan motor is running.

Check that the EcoLet™ is vented correctly and that the vent pipe connections are airtight.

Check that the vent pipe is unobstructed by bulking material, insects, dust, or toilet paper.

Check that the front cover for the humus tray is properly secured.

Check that strong cross-draughts, open windows, or room extract fans are not overcoming the suction of the toilet vent fan.

If excess moisture is present in the indicator hose or tray, increase the heater setting and review use conditions.

An odour is present outside the building but not inside

Recommended course of action.

Check that the vent pipe extends adequately above the roof line and terminates correctly.

The exhaust should be relatively low in odour. Noticeable external odour can be caused by underperforming composting, poor ventilation, or excessive moisture in the system.

Odour is associated with the end-product

If the finished product from the removable tray is not light, friable, and earthy-smelling, the system may not be achieving complete composting.

Recommended course of action.

Review airflow, heat, moisture balance, bulking routine, and user loading.

Fan is making a lot of noise

Recommended course of action.

Check that the fan is not obstructed by bulking material or paper. If it is not obstructed, the fan or bearings may require service or replacement.

Liquid in indicator hoses or excess moisture in the upper composting chamber

Recommended course of action.

If you see liquid in the indicator hose(s), control it by adjusting the heater setting and reviewing use conditions.

If liquid is visible in the overflow hose on the left-hand side of the toilet (when facing the unit), do not open the front cover until the level has been reduced.

• Check the unit is plugged in and there is power to the plug.
• Check the fan is running continuously.
• Check that the heater setting is appropriate for the moisture level and conditions.
• In the upper composting chamber, ensure the bulking mix is not compacted. Use the hand rake if required.
• Ensure the toilet is being used within its practical capacity.
• Make sure you are using the correct bulking material and adding enough.
• Ensure there is sufficient ventilation to the toilet.

Compost tank is getting too full

Recommended course of action.

Check that there are not too many people using the toilet for the site conditions.

For the EcoLet™ 25a / 65a range, allow the lower tray to remain in place long enough for continued composting, and empty it only when the chamber level reaches the upper mixing arm or when normal tray service is due.

The composting process does not seem to be working

Compost pile appears too dry

Recommended course of action.

The compost is too dry when it becomes hard, paper stays on top, and material does not mix into the pile properly. Turn the heater setting down or off to reduce dryness. If the compost remains very dry, sprinkle water over the compost gradually while breaking up hard areas with the rake.

Compost pile appears too wet

Recommended course of action.

Check that the fan is running and that the heater setting is appropriate for the conditions.

• Mix extra approved bulking material into the compost.
• Increase the heater setting until the liquid level has been reduced.
• Check that the toilet has not been overloaded with too many users.
• Check the vent installation and insulation if condensation or cold conditions are contributing.

There seems to be too much toilet paper visible on the top of the pile

Ensure sufficient bulking agent is being added regularly. Consider that some users apply much more toilet paper than others.

Recommended course of action.

Dampen and lightly agitate the top of the compost pile if needed so the paper can mix into the active composting mass. Also check that the pile is not too dry, too cold, or short of bulking material.

Climate – temperature & atmosphere conditions

WCTNZ® makes every attempt to match you with the right system for your site and climate conditions, but changing weather patterns and room conditions can still affect performance.

In colder climates, systems can slow down in the rate of processing. Check that the surrounding room temperature and vent arrangement are suitable for the model being used.

Undesirable insects in the compost tank

If insects have entered the compost, review airflow, moisture balance, and cover material use. Keep a fresh layer of bulking material over exposed solids and maintain strong directional airflow through the vent system.

Separera Mini – quick reference

Bad smell in the room

Check that the fan is running, the vent line is sealed and unobstructed, the solids chamber is fitted correctly, and the room has adequate make-up air such as a door undercut or vent.

Slow urine drainage or salt build-up (UD-S)

Flush the urine bowl with water regularly and check that the urine line has continuous fall away from the toilet. For longer runs, transition to a suitable larger drain line as recommended in the manual.

Indicator not showing normal on UD-C

Remove and reseat the urine container correctly, reconnect power, and confirm the indicator returns to normal.

When to ask for help

If the unit has persistent odour, abnormal liquid behaviour, damaged electrical parts, repeated fan issues, or poor performance after the checks above, contact WCTNZ® with the model, serial number, and a clear description of the issue.

WCTNZ® | Waterless Composting Toilets NZ Limited | Copyright 2026 ©