Drain Flies & Larva in Toilet

Get Rid of Flies in Your Toilet

No one likes flies. Now, imagine sitting down on your throne to take care of business and having these drain flies buzzing in the bowl beneath you. Not fun.

Assuming you have properly identified the flies to be Psychodidae (moth or drain flies), then your path forward is clear. You need to remove any buildup inside of your drain pipes and standing water.

Toilet Wax Seal

Drain flies breed in the buildup in pipes. While it is less common for them to appear in a toilet, it could be they are entering the bathroom through a faulty seal between the toilet and sewer flange. This might indicate they are breeding lower down in the pipe and flying upwards.

Drain flies generally are found near their breeding areas, so if they are appearing in your toilet or bathroom, that is the best place to start.

toilet flange wax seal

Remove buildup in Pipes

Any plan to fight drain fly infestations needs to include multiple methods. Removing scum buildup is extremely important for preventing ongoing issues. Killing adult drain flies will only provide the appearance of success.

Drain fly eggs hatch in 32-48 hours and lead to the larval and pupal stage.

Now, this is where it can get tricky. In most cases, cleaning a drain or pipes is as simple as pouring hot water down the drain and then using a scrub brush to remove buildup. This is generally followed by a drain gel to remove the remaining buildup.

The piping below your toilet is somewhat complex and you will not likely be able – or want – to start pulling pieces apart. You can try to pour drain cleaner to clear blockages, and then try drain gel such as Green Gobbler Drain Gel to help remove buildup and kill flies.

Lastly, to prevent adults from laying more eggs, spray Gentrol IGR into the drain/pipe.

A Break in Your Sewer Line?

In older homes, this is more common. Shifting soil, corrosion, root infiltration, grease buildup and debris can all cause issues that are extremely intensive to correct. If you suspect a mainline break or crack, you may need to call a plumber to confirm your suspicions.

Sewer line issues are usually accompanied by backups, soggy grass and a stench.

It is more common to see drain flies in the basement if a sewer line is broken beneath a slab. In this case, correcting the issue requires an expert who can 100 percent confirm the issue, break the floor, replace the piping and remove the contaminated soil.

Failing to complete all steps can result in an infestation of contaminated soil.

However, this should really only be on your mind if you see other signs, such as those mentioned above.

Check your Tub and Sink

It could very well be that the flies you see are actually coming up through your shower drain or bathroom sink. These areas tend to experience drain fly issues more often and are easier to treat.

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Article Reviewed By:

Dakota S. MS in Biology

Dakota holds a Masters of Science in biology/biological sciences, with an emphasis on entomology and parasitology. An accomplished researcher and writer, Dakota has completed numerous research papers and published peer-reviewed literature. Notable accomplishments include the study and documentation of new structures not previously known to be fluorescent in Ixodida (ticks).