How To Get Rid Of Sewer Flies In RV (12 Methods!)

One of the most common and peskiest pests that an RV owner can face is the bug with the Latin name of Clogmia albipunctata, better known as sewer fly, drain fly, bathroom moth midge, and so on. Though they are not biting insects, nor are they known for transmitting diseases, they are a nuisance. 

They prefer to live and breed around sewage drains and treatment plants, swamps, and generally in the shaded areas with stagnate water rich with decomposing organic matters. Such areas exist in the RVs, first and foremost the wastewater tanks and the drains. 

Getting rid of them starts with identifying whether your RV is actually infested by them and what is the source of them. Only then you can be certain that eradicating them can be successful and what measures you must take to prevent them from returning. 

What’s Attracting Sewer Flies To Your Rv? 

All pests you may encounter in your environment are attracted by three things, food, breeding conditions, and shelter. Sewer flies can enter your RV looking for food too, and the good thing about this is that if you notice them in your RV, it doesn’t mean that it is infested by them. 

But to understand how to get rid of them or prevent them from colonizing your motor home, you must first know why they can show up near you. 

Shade During The Day 

Insects that like direct sunlight and heat of the day are very rare, and sewer flies are not among them. As such, they will look for a place to hide from the sun. As they are not very good flyers, they will look for a place near their breeding grounds. 

Because sewer flies usually live and breed around places with rotting organic matter and stagnant water, RV campground sewer hookups are places almost guaranteed to find them. So, if you notice them inside your mobile home during the day, they very likely are hiding from the sun. 

Light During The Night 

Many insects that prefer to live and breed in warm and damp places, as sewer flies do, are indirectly attracted by lights during cool nights. Most commonly used lightbulbs around RVs are emitting both heat and UV light, which actually attract many insects. 

If you see sewer flies in and around your RV during the nighttime, it could be because they are attracted by the lights and that your recreational vehicle is not infested by them. So getting your motor home rid of them can be fairly easy. 


Adult sewer flies can live up to 12 days by only drinking water. But where is moisture, there are potential sources of food and perfect conditions for laying the eggs. Adult insects prefer to feed on the nectar of flowering plants, which they find by sensing the moisture in the air. If your vehicle is near their colony, they can be attracted by flowers in your RV. 

But moisture also indicates the presence of places that are an appropriate breeding ground for them. 

Decomposing Organic Material 

Dark, humid places with decomposing organic matter, or bacterias and fungi which sewer fly larvae eat, are places where sewer flies lay their eggs. Improperly sealed or leaking shower pans, “P” traps, and wastewater sinks and tanks are places in RVs that are favored by these insects. 

How To Get Rid Of Sewer Flies In Your Rv? 

Depending on whether you have a sewer flies infestation or invasion, you should decide on what are the necessary steps in eradicating them. If they have only flown in from the outside, just killing those that are apparent could be enough to deal with these pests. 

But in any case, it is a prudent decision to check places where they could have laid their eggs and take measures to prevent their infestation. The best way to get rid of them is to prevent them from becoming a problem by destroying all potential breeding sites. 

Aerosol Insecticides 

In case that you only need to destroy adult sewer flies that have entered your RV from outside, various bug sprays are good enough solution. For such short-term solutions, the most popular are sprays containing pyrethrins and their analogs, pyrethroids. Pyrethrins are naturally occurring compounds extracted from several types of chrysanthemum flowers. Because of this, it is considered an organic pesticide. 

Besides these two types of insecticides, there are numerous other bug sprays that you can use. Some general rule is that if such an insecticide is toxic for mosquitos and house flies, then it is appropriate for dealing with sewer flies too. 

Boric Acid Spray 

One of the most popular home insecticides for controlling sewer flies is spraying a water solution of borax. But in reality, it is not an effective bug killer. The confusion comes from the fact that borax is a compound of boron that is commercially sold in the form of a white powder. 

On the other hand, boric acid is a relatively effective and relatively safe insecticide that can kill insects that groom themselves. Boric acid is commercially sold in the form of a white powder, and it is also a compound of boron, but when insect ingests it, it is very toxic for them. Because of this, you will find them as an active ingredient of many commercial insect traps. 

For killing adult sewer flies, you will need to create a 5%-10% solution and spray it on them directly. 


Either commercial or homemade fly traps can be used for controlling the population of adult sewer flies. The easiest one to make from household items is a trap with apple cider vinegar. All you need is some vinegar in a glass or similar container; a quarter of a cup is enough that you will close with plastic wrap. 

You will need to pierce some holes in the plastic wrap and place the trap near the area where you have noticed the flies. The smell of apple cider vinegar will attract them, and they will find their way into the trap. Unfortunately for them, escaping from it is not so easy. 

Drain Insecticides 

In case that the sewer flies have infested your RV’s sewage, you will need to take more drastic measures. On the market, you can find many specially formulated insecticides intended for use in drains. They are mostly used by pouring or spraying them inside of your drains, and thus they create a toxic barrier that is deadly to sewer flies that try to escape from your drains. 

A drawback of these insecticides is that they are actually just a short-term solution, as they usually do not kill larvae, nor do they make your drains long term unsuitable for flies to inhabit them. 

Drain Repellents 

Another potential solution for the problem of sewer flies infestation is various insect repellents intended for use in drains. They are usually based on citronella oil, an extract of lemongrass, which is a non-toxic bug repellent. These repellents most commonly have a gelatinous formulation and need to be poured into drains, and thus they prevent sewer flies from exiting through drains. 

The problem with this solution is that it only makes the infestation less visible. Both adult and larvae of sewer flies will remain inside the pipes and tanks. While they will be effectively prevented from invading your living space, you will still need to deal with them in their preferred living space. 


Probably the cheapest way to kill adult sewer flies is cold. All you need is to empty your tanks and leave your RV exposed to temperatures below freezing for at least 48 hours. But that is easier said than done for the majority of RV owners, and some more readily available remedy is a better solution. 

Many dead flies isolated on white background

How Do You Get Rid Of Sewer Fly Larvae? 

Just killing adult flies is not enough to permanently get rid of them. Adult flies can live up to 12 days, but already on the second day of their life, they are ready to lay eggs. Female adults can lay anywhere between 30 and 100 eggs, from which, over the next two days, larvae will hatch. 

They will spend in this form up to fifteen days feeding on decomposing organic matter, algae, and other microorganisms. When ready, larvae will cocoon, and a new adult sewer fly will emerge, which forces you to deal with them every three weeks unless you destroy both existing larvae and their breeding grounds. 

Flush The Tanks 

Sewer flies look for damp places rich with decomposing organic matter to lay their eggs, and that’s where you will find their larvae too. While your drains and pipes could be slime-free, your black water tank is a perfect place for them to thrive. If you notice sewer flies in your RV, thoroughly cleaning the black water tank is a must. 

The exact method of flushing the tank is not crucial, as long as you flush out all the content of it, especially the grime and slime that can accumulate on its upper inner side. 

Pipe Cleaners 

Sewer flies have very fine hairs covering their body and wings, which serve as a water repellent and protect them from drowning. This makes them able to fly up from the black water tank and find the slime that builds on the inside of drain pipes, creating a perfect spot for laying eggs. 

Because in the case of sewer flies, infestation larvae can be present in this layer of slime, one solution is to remove it with pipe cleaners. You will find available many commercial chemical products for this, but you will still need to flush the tanks. 

Enzyme Drain Cleaners 

If you are looking for a more eco-friendly solution for dealing with larvae, enzyme pipe and drain cleaners are your best option. Almost all enzyme cleaners are based on chemical compounds extracted from plants and thus are a natural solution for this problem. Enzyme cleaners that are commercially available contain either bacteria or plant enzymes that will speed up the decomposition of organic matter in your RV’s drains. 

Enzyme drain cleaners will both help you remove organic material from your drains, along with it the sewer fly larvae, while being less aggressive on the pipes and other parts of the waste system. 

Tank Additives 

Though many people do not like to use tank additives, the reality is that they are very helpful in dealing with sewer fly larvae. Their function is to speed up the degradation of organic matter inside your black water tank. This way, the larvae will be robbed of the food source, which will kill them. 

Another advantage of the tank additives is that their regular and proper use is an excellent prevention of sewer flies infestation in the first place. 


While there are many recipes and instructions for using bleach to kill both adult and larvae of sewer flies, in reality, they just don’t work as advertised. But that doesn’t mean that it isn’t a potential solution, just that it doesn’t work the way you can read in various articles. 

Bleach is not toxic for sewer flies as much as it works as a degreaser, and thus robbing larvae of their food source. Even its antimicrobial effect is present because it melts lipids that encapsulate both bacteria and viruses. 

In other words, bleach works similar to pipe cleaners and tank additives but has a drawback that when combined with vinegar and other acids, or ammonia-containing compounds such as urine, it produces chlorine and chloramine gases, respectively. Both of these are very toxic gases and must be used with special care. 

Mechanical Cleaning 

Getting rid of sewer fly larvae boils down to getting rid of the matter in which they reside. If for any reason you are unwilling or unable to use any chemical cleaning method for your drains, pipes, and tanks, mechanical cleaning is your only option. Various brushes and similar devices intended for cleaning drains and pipes exist. 

And also, much newer RVs already come equipped with tank wands and similar devices intended for this exact purpose. The only thing you should pay attention to is that the water pressure is sufficient for washing all of the stuff stuck to the pipes and walls of the tank.  

Getting rid of the sewer flies in your RV can be a challenge if you don’t do it properly. Adult flies can be killed by various insecticides, both synthetic and natural. But if your black water tank and drain pipes are infested by them, just killing adult bugs is not enough; you will need to get rid of larvae too. 

Dealing with larvae is easiest done by removing the matter in which they are, in other words, thoroughly cleaning the whole sewage system of your RV. 


Now you know what’s attracting sewer drains to your RV, how to get rid of them, and also how to get rid of sewer fly larvae! If you liked this article and found it helpful, then make sure you check out the rest of the website! Otherwise, have a great day!

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