Shoo Fly (Don’t Bother my Composting Toilet)

One of our most frequently asked questions is “will there be bugs?” While we’ve designed a chamber system that minimizes the risk of creepy crawlies there are preventative measures you can take to further distance yourself from those pesky bugs.

Composting is all about maintaining a comfortable environment for the microbes and unfortunately, their ideal conditions can also be facilitative for insects; so we’ve taken care to design a system that is difficult for them to infiltrate. The flyscreen mesh on the ventilation caps and the constant airflow from the fan creates a draught that hinders the fly's ability to hover and settle on the compost pile comfortably. The mesh obviously is also a barrier between the compost and the outside world that, with the double-walled design, prevents bugs from sneaking in while your chamber is collecting or resting. 

But as well as we think we’ve done there is the possibility of a bug problem when conditions are right - when it’s hot and humid especially. We’ve created this comprehensive guide for you to identify your flies as well as preventative and reactive measures against them.

What kind of flies might be attracted to my composting toilet?

What can I do to prevent flies from getting into my compost?

What do I do when I see flies in my compost?


Know Thy Enemy

It's going to be important to identify the type of flies that you are seeing, because they will all have different habits and life cycles. Depending on the type of fly, your tactics may change. For example, you can’t just treat the composting toilet but also surrounding areas where they could be breeding or feasting. 

That is why the first step is to identify what type of flies are hanging around your compost toilet; the most common pests that we have encountered are Fungus Gnats, Vinegar Flies, and Soldier Flies. Below is a quick reference guide to the key differences between these breeds of flies:

Fungus Gnats

Vinegar Flies

Soldier Flies

What do they look like?
Small flies up to 3mm, black or dark grey in colour
Small flies up to 4mm, yellow or brown in colour with distinct red eyes
Large flies up to 22mm, dark blue or black in colour
Where do they lay eggs?
In wet soil and organic material (i.e.decomposing, fermenting products and waste components)
Moisture and liquid residue (i.e. damps sponges, mops, small pools of water, constantly damp places)
Dryer surfaces near organic material, especially small cracks and crevasses
What is the average lifecycle?

28 days

10 days

44 days

What do they eat?
Fungi and plant roots
Bacteria and yeasts (usually associated with rotting fruit)
Rotting food and manure
Why are they attracted to my composting toilet?
They will be attracted to the moist composting pile to lay their eggs. So treating the compost pile will affect the whole lifecycle.
But the compost pile isn’t a reliable food source because there shouldn’t be any plant matter and only small amounts of fungi (part of the microbe mix).
The adult flies will be attracted to the bacteria and yeasts of the composting pile.
They will lay eggs nearby in any damp places, such as the leachate drain or condensation in the ventilation pipes.While hovering around your compost pile and using it as a foodsource.
They will be attracted to the compost pile and the humanure as a food source. But as they are large in size, they cannot easily enter and leave the chamber.
They may lay their eggs nearby, in the small cracks like the crevasses of a wall.While trying to visit your compost pile as a foodsource.

Methods and Products for keeping flies out

General Compost Toilet Maintenance

Firstly and most importantly: do not put food scraps into the toilet as that will be a very attractive food source to the flies and actively attract them to your pile! It’s as simple as that; we cannot recommend adding food scraps to your toilet’s composting pile for several reasons but the first and foremost is that it will attract bugs and flies moreso than anything else.

Next up is the fan and ventilation. Flies don’t like the constant airflow from the fan because it makes it difficult for them to settle; it’s very common to see an infestation begin just after a fan has stopped working. It’s a safe bet always to have a spare fan on hand, so you have a consistent airflow with no fluctuations. 

The ventilation piping should be clear of blockages, including reducing horizontal sections where condensation can pool. There should also be no dips or loops in the flexi hose - trim it to length if required. Make sure the vent cowl, or equivalent, is secured to the vent pipe correctly, and remember that vinegar flies can penetrate standard flyscreen so try to use midge mesh where possible. 

Wet conditions are very attractive to flies, so once you’ve checked the ventilation pipes it’s time to check the moisture content. If the composting chamber is full of liquid and everything is soggy, this can be indicative of a drainage issue. Otherwise, try adding some extra bulking agent and running the system dryer than you previously were to try and dissuade the flies. 

Using fly traps can catch adult flies before they have a chance to lay eggs, which helps disrupt the breeding cycle; but they are also useful to locate where flies are congregating as well as creating a benchmark to gaue any increase or decrease in numbers.


Be careful what products you use around your composting pile. Just like antibacterial cleaners will kill your culture of microbes, so will some insecticides! 

The best preventative measures are Diatomaceous Earth and Yates Tomato Dust because they will create a hostile surface for the flies. When using these you’ll want to follow the safety instructions first, turn off the fan and add a small handful to the chamber from the pedestal. Having the fan off will give the material a chance to settle instead of immediately being disturbed by the airflow; this will prevent the flies from landing on the compost heap and laying eggs. The results of this may not be apparent immediately; instead, the best results will be after a few days left undisturbed so it is more effective on out-of-service chambers. 


Removing Flies from Compost

Our best recommendation to react to an infestation of flies is a pyrethrum-based insecticide. Direct contact with a pyrethrum-based product will kill flies, without harming your culture of microbes! This, in conjunction with good maintenance and the above preventative measures, will start to reduce the number of flies. 

Just remember that you need to treat the entire lifecycle and treat the surrounding areas. Because it only takes a few flies to lay eggs and the population starts to increase again.

In the In-Service Chamber

Firstly, you want to turn off the vent fan temporarily, otherwise, the insecticide you're putting in the chamber will get sucked out.

Liberally spray into the bowl and the chamber. 

Immediately cover the toilet bowl, this is most effective when using plastic wrap to seal the opening. This traps the insecticide spray inside. 

Leave for at least 10 minutes to let the pesticide settle and affect all the flies inside. Then you can turn the fan back on.

Do this every day until you have broken the lifecycle of hatching flies. 

In the Out-Of-Service Chamber

If you have the ventilation connected to your out-of-service chamber, follow the in-service chamber instructions.

Place a layer of diatomaceous earth over the top of the pile, to create that hostile surface that harms the flies. 

Follow this with the insecticide spray.

When you're closing the chamber back up, make sure to spray any potential hidey holes that the flies may also be in nearby as the flies won't only be in the compost.


In the spirit of reconciliation, Ecoflo Wastewater Management acknowledges the Traditional Custodians of this Country. We pay our respects to their Elders past and present and extend that respect to all Aboriginal and Torres Strait Islander peoples today. 




Ecoflo was the first company in Australia to sell composting toilets certified to the rigorous quality testing of Australian Standards. If you want to be certain your composting toilet has adequate capacity and is safe, you need a waterless composting toilet certified to the tough performance criteria of AS/NZS 1546.2:2008.

Shop our range of certified toilets here