How to get rid of flies in a composting toilet

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This article discusses how to get rid of flies in a composting toilet, and avoid them in the future.

The Thinktank Waterless Toilet is airtight under normal operating conditions. Therefore, flies are very rarely a problem.

However, if you have another brand of toilet, you may encounter a problem with small flies finding their way into the toilet.

The Thinktank Toilet is airtight

Flies are rarely a problem with the Thinktank toilet, as it is much more tightly sealed than other toilets.

Eliminate the Source of Flies

The first step is to eliminate potential sources of flies in the home. The toilet does not produce flies, and there should not be flies or fly eggs in human waste. That means the flies came in from somewhere else. Fruit bowls are a big culprit. Once in the home, flies will be attracted to the toilet, where they lay eggs and multiply. Before leaving your cottage, eliminate all possible sources of flies, including garbage (not even an apple core should be left behind) or compost.
How to get of flies in a composting toilet. The Thinktank has a powerful fan on the exhaust port.

The Thinktank has a powerful exhaust fan, and an intake fan should you need it.

Make Sure the Fan is Working!

You should be able to feel slight airflow at the exhaust vent. If not, clean the screens (there may be screens inside the toilet and at the exhaust) and if possible vacuum the fans. Check again. With some toilets you can see if the fan blades are turning.

Make the Toilet Unattractive to Flies

Nature's Head fan housing

Nature’s Head fan housing needs to be removed to access the fan

The second thing you do is make the toilet unattractive or unavailable to the flies. Clean the toilet very well inside, in every nook and cranny, with something that will kill fly eggs like a mild bleach solution. Water and vinegar will not work.

Don’t get the fan wet. With the Nature’s Head you can remove the fan housing and hose it all down outside, after using the bleach. However, the Separett fan housing is a bit of work to remove, so it’s best to clean the toilet with the fan housing in place. (Flies are generally not a problem with the Thinktank toilet due to the airtight design.)

Add Diatomaceous Earth

Add about 5 cups of diatomaceous earth to toilets like the Nature’s Head, or add a cup per week to a toilet with a removable container. You may have to experiment a bit for the optimal quantity.

how to get rid of flies in a composting toilet with diatomaceous earth

diatomaceous earth

Diatomaceous earth is a naturally occurring, soft, siliceous sedimentary rock that is easily crumbled into a fine white to off-white powder. It is a very good natural insecticide. This will solve the fly problem 99% of the time. It is not expensive and commonly available.

Additional Tips

Contrary to what you may have read elsewhere, you should NOT replace the screen in your toilet vent with no-see-um mesh. This will reduce the airflow to almost nothing.

You should not need flypaper or insect traps near the toilet. The problem is inside the toilet, not outside.

Once you do these things, I am quite sure you will have no more fly problems. Cleanliness and removing the source of flies is by far the most important step to get rid of flies in your composting toilet.

Read more reasons why the Thinktank is the most fly-proof, advanced urine diverting toilet.

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5 thoughts on “How to get rid of flies in a composting toilet”

  • Reply ↓
    Vanessa

    I tried for about 2 years to get rid of gnats in my compost toilet. At last I’ve found something that works. Neem oil, you can get it at Lowes for like $7 in a spray bottle. I just drench my compost in it once a week.

    Once upon a time I would kill about 60 gnats a day and still have swarms everywhere. Now, I see about 2 a day.

  • Reply ↓
    Karen Gruhl

    Hello,
    Our composting toilet is at our camp (cottage). It is non-electric, so no fan and also in its own separate building (not in the cottage). I think they are fruit flies but am perplexed as to why they were attracted to the toilet? We have two composting toilets and only one has flies. Any suggestions? I can try bleach solution. Thanks.

    • Reply ↓
      Richard Post author

      Please see my page on how to get rid of flies in a composting toilet. I don’t have any non-electric toilets, so I’m not sure what brand you are using. I tell people that they can try using the toilet with a vent only (in an outhouse) but there is no guarantee of success. A fan is often required, even in an outhouse – and 100% of the time in a home. I know many people don’t want to power their toilet, but this can result in odor and insects. I would not believe any claims from sellers that you can have a composting toilet without a fan. Some toilets don’t even have vents (which is beyond ridiculous).

  • Reply ↓
    Trudy Bradt

    Hello….we have a moth problem with our composting toilet. They seem to be hatching in it. We see them flying up out of the toilet and we’re greeted with many of them flying around the room every time we open the door. We are wondering what we can safely spray in it to kill them that won’t harm the way the toilet works. Thank you in advance.

    • Reply ↓
      Richard Post author

      Follow the same instructions as with flies. You should clean out the toilet. Moth balls, insect spray etc. will not harm the toilet.