Holding tanks and wastewater management can be an unsavory part of RV camping. Add squirmy critters to the mix and that causes most people to shudder with discomfort.
What causes sewer flies and their offspring to come out of the RV toilet in the first place? In this guide we will address where sewer flies come from and how to get rid of them without using caustic chemicals that will destroy an otherwise healthy RV holding tank.
Key Points About Sewer Flies
- Sewer flies are often found in RV plumbing and sewage systems, and while they are harmless, they can be annoying.
- They feed on organic decaying matter (like human waste and toilet paper).
- Keep sewer flies out of your RV by making a P-trap in your discharge hose with water in it, or by keeping your RV tank valves closed.
- Get rid of sewer flies by thoroughly deep cleaning and rinsing your RV black tank, or by trapping them.
The Problem with Sewer Flies
Sewer flies, also known as drain flies, are a species of flies that are often found inhabiting plumbing drains and sewage systems. While they are harmless to humans, they are typically frustrating and an unwanted annoyance in your RV.
Sewer flies live in aquatic environments, or sludge-based habitats, including septic systems, holding tanks, and bathroom sinks where they feed on organic decaying matter, like poop and paper, and polluted water. Because sewer flies eat organic matter and sewage, the septic septic system in your campground may be an ideal breeding ground.
Sewer flies lay their eggs in water and once hatched, the larvae look like small worms. Some RVers report seeing these worms emerge from their black water holding tanks, crawling up the inside of their toilet.
Now that you have more information than you probably ever wanted to know about sewer flies, the question is how do you get rid of them!
False Remedies to Get Rid of Sewer Flies
Not every common solution is as effective as it seems, and some popular remedies may only mask the problem rather than address what's attracting sewer flies in the first place.
Bleach
A common misconception is that pouring bleach down the drain is the best way to eliminate sewer flies. Unfortunately, this rarely takes them out completely.
Although bleach may get rid of some of the larvae, bleach cannot permeate through the thick build-up which resides on the walls of a holding tank where the eggs are laid. Additionally, the bleach will also kill the bacteria used for waste breakdown in a healthy holding tank.
Boiling Water
Boiling water and pouring it down into the black tank has also been recommended from various online resources. However in order for that to be effective, the boiling water would need to fill nearly to the top of the holding tank, and getting 40 gallons of boiling water into your black tank is asking a lot! This recommendation is best for households and not RVs.
Harsh Chemicals
We DO NOT recommend using any caustic chemicals such as bleach, Drano, ammonia (especially when used in conjunction with bleach as it can make a toxic gas) or any antibacterial soaps.
These will do far more harm than good as they will kill all of the good bacteria needed for waste breakdown in the tank, which will lead to further problems, like waste buildup, clogs, and persistent toilet odors.
Getting Rid Of Sewer Flies In Your RV
The best advice we can offer is to stop them long before they get a chance to move into your RV holding tanks. To accomplish this, simply:
1. Eliminate the food source that is attracting sewer flies to your black tank by deep cleaning your tank withGet rid of sewer flies in your RV with Unique Clean-It, and rinsing your tank very thoroughly.
A 2. Form a bend in the sewer drain hose as it leaves the RV to make a P-trap and pour water into the P-trap.
Learn: How and Why to Add a P-Trap to your RV Sewer Hose
3. A high quality holding tank treatment to keep sewer flies from having a food source
To prevent sewer flies, make sure you keep a P-trap in your discharge line at all times and treat your tanks with a high-quality waste digesting treatment like RV Digest-It Ultra.
With a clean black water holding tank and plumbing lines, sewer flies have no food source and nowhere to lay their eggs, so they will stop inhabiting your tank.
A Home Remedy For Drawing Out Sewer Flies
If you have sewer flies in your holding tank, one way to draw them out of the tank is to mix a solution of water, sugar, apple cider vinegar, and a few drops of Dawn Ultra in a bowl, and cover with plastic wrap.
Then, poke a few holes in the plastic wrap and place the bowl near your toilet. This solution will attract the flies and the holes will allow the flies in but will not let them out and they will die. This should be kept as close to the RV toilet drain as possible.
To accomplish this, turn off the water supply to the RV toilet to keep water from entering the toilet bowl.
Hold the flush pedal down all of the way, until all of the water is drained from the bowl. Release the flush pedal and place the bowl with the solution in it overnight (sewer flies are nocturnal) near the toilet bowl.
The next morning, you will find a bowl full of sewer flies! Dump out the contents of the bowl, turn your water supply back on and you are all set!
We hope this has helped you understand sewer flies, and how to get rid of them, a bit better!
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