How to Get Rid of Sewer Flies in an RV?

Are you having an issue with sewer flies inside your RV? These pesky nuisances can make living on your rig a real nightmare. There’s nothing worse than walking into your RV bathroom and being swarmed by these small creatures.

This step-by-step guide will ensure sewer flies never wreak havoc on your mobile home again. If you follow this method, I promise your RV will return to a blissful mobile home.

What You Need to Get Rid of Sewer Flies?

The only thing needed to kill those pesky sewer flies is one of the following cleaners:

  • Bleach
  • Enzyme Cleaner

Bleach is a more useful option and our chosen method. But there are concerns with using bleach in your black tank. The first issue is its possible interaction with ammonia to produce chlorine gas, which can be fatal to humans.

You must make sure never to mix bleach with other cleaners and avoid this situation from happening. Bleach can also be corrosive at high concentrations. As a result, it can break down your black tank’s seals located at the value.

This issue could be a problem considering our method will leave quite a bit of bleach in the tank for extended periods. If you’re worried about the black tank’s seal durability, enzyme cleaners will be an effective alternative.

These cleaners work by attacking the organic material where the flies lay their eggs. If you get rid of this layer, the flies will no longer have a food source. The using method is remarkably similar to these five steps below, but it requires several applications.

5 Steps to Get Rid of RV Sewer Flies

Step 1: Close Your Tank Dump Values

You’ll want to locate your RV sewer hookups outside and close the dump valves. In fact, you should only open the black tank dump when you’re actively dumping it. It’s key to let the waste build up inside your tank. This action will help avoid the dreaded poop pyramid.

As for the grey tank valve, I suggest leaving it closed until your tanks need dumping. It’s worth the effort of going outside and opening the drain when washing dishes, taking showers or doing laundry. It’ll create a more effective cleansing of those sewer flies and their larvae inside the tanks.

Step 2: Empty The Black Tank of All Contents

Once you’ve closed the black tank value, it’s time to empty everything inside of it. You’ll want all the urine and poop out before beginning the next set of steps. It’ll put a focus on those fly eggs and larvae inside your tank, which will effectively stop the reproduction cycle.

Step 3: Fill The Tanks With Bleach

I suggest going with the same concentration used when sanitizing your RV’s fresh water system. You should dilute ¼ cup of bleach into one gallon of water for every 15 gallons of your black tank’s capacity. Fill the black tank up to the very top for the best results.

RV sewer flies 2

This action should take away the fly larvae’s favorite developing stop. The top happens to be where there’s enough organic material, but there isn’t too much water or tank treatments capable of killing them.

Step 4: Let the Black Tank Marinate

It would be best if you let the bleach and water sit inside your black tank for an extended period. I suggest at least four hours just like when you sanitize the water system. But if you can, try letting the bleach sit overnight. It’ll increase the bleach’s odds of penetrating those eggs and larvae inside your black tank.

Step 5: Drain and Rinse

After letting the bleach soak in, it’s time to drain out your black tank. Make sure to give a good rinse, as well. A thorough rinse will ensure the formation of chlorine gas doesn’t occur. If your RV has a backwash system, I recommend using it.

RV owners who don’t have a backwash system can use this alternative:

Installing a Dual Flush Pro with Rinse Value: Replacing your current valve with one of these doesn’t require much DIY skills. It will thoroughly flush out your black tank without much issue.

RV sewer flies

Get Rid of Sewer Flies Easily

Did you enjoy our tutorial? Following these steps should’ve done an efficient job of getting rid of your sewer fly problem. Your rig shouldn’t have a single issue with RV sewer flies going forward.  After all, it sure did solve my issues with these annoying little insects.

But please, let me know how well it works for you in our comment section. If it did solve your problems, don’t hesitate to share the article with your fellow RVers!

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John Miller

John Miller is a cars enthusiast who loves writing anything related to automobiles. He is a passionate blogger writing for and other auto blogs