Go Back   iRV2 Forums > MOTORHOME FORUMS > MH-General Discussions & Problems
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
Thread Tools Search this Thread Display Modes
Old 11-17-2017, 12:02 PM   #1
NINK's Avatar
Monaco Owners Club
Join Date: May 2011
Posts: 93
Gnats from RV Black Tank - Solved!!! (I think)

We have had an increasing problem with Gnats (Fungus Flies) coming up out of the black tank that has been going on for a couple of years now. We have tried all kinds of solutions, including many posted on various threads on this forum. Bleach, additives, Happy Camper, flypaper, wine traps, etc, etc. To no avail, although, the wine traps (a little wine in a dish with some cling wrap with a small hole in it) do catch them.

Draining an flushing the black tank every other day works fine, but, we are not always hooked up to sewer, as we stay in a lot of state parks, etc. By the 3rd day, they have always returned.

However, I recently tried this product:


I drained and flushed the tank as usual, put a small amount of water in the tank, maybe a quart or so, and dropped in one of the packets. It has now been 9 days without emptying the black tank (and counting) and have not seen a single gnat!!!!

I've been going through the phases from, I'll try anything, to hope, to disbelief to "I'll be damned!"

I am posting this to a new thread in the hope that some other people with this problem may try this, and report back on the results, just to make sure that some other factor is not at work in my case. If you try this and it works, or does not work, please post your results either way.

Bob, Janice & Guinness the Hound
2001 Monaco Executive (MuttRHome)
with Saturn Vue in tow
NINK is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 11-17-2017, 03:08 PM   #2
Senior Member
BFlinn181's Avatar
Gulf Streamers Club
Join Date: Jan 2012
Location: Cincinnati
Posts: 16,264
I'm glad you find success with this product, but I am surprised. The link goes to small packets of nematodes that are to be placed in potting soil to prevent fungus flies in plant pots. I've not heard of fungus flies in black tanks, they are generally called flies or gnats. They can be hard to get rid of because the adult flies can be killed off for a day or two but then the eggs and larvae in the tank mature and you've got them all over again.

The nematodes, or roundworms, in the packets are to be added to moist soil where they will feed on the eggs and larvae. Putting them in a black tank might work, but I'd be surprised if they didn't drown since they normally live in soil, not liquid.


Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI
BFlinn181 is offline   Reply With Quote
Old 11-17-2017, 05:14 PM   #3
Senior Member
Tony Lee's Avatar
Join Date: Sep 2012
Location: Peru heading for Brasilia, Brazil
Posts: 2,122
Drain flies, sink flies, filter flies, or sewer gnats are small true flies with short, hairy bodies and wings giving them a "furry" moth-like appearance, hence one of their common names, moth flies.
How would they get out of the black tank in enough numbers to be a problem.

Usual place they breed is in traps under sinks, basins and showers.
Tony Lee - International Grey Nomad. Picasa Album - Travel Map
RVs. USA - Airstream Cutter; in Australia - MC8 40' DIY Coach conversion & OKA 4x4 MH; in Germany - Hobby Class C; in S America - F350 with 2500 10.6 Bigfoot camper
Tony Lee is offline   Reply With Quote
Old 11-18-2017, 11:04 AM   #4
NINK's Avatar
Monaco Owners Club
Join Date: May 2011
Posts: 93
Originally Posted by Tony Lee View Post
How would they get out of the black tank in enough numbers to be a problem.

Usual place they breed is in traps under sinks, basins and showers.
What you describe is not what I have had. This are small black gnats that are extremely aerodynamic fast fliers and very elusive. They know when you are hunting them or even looking at them and will move into a corner, crack or crevasse to avoid your attempts to kill them. They hatch in the black tank and come out either when the toilet is flushed or through an air vent that exists in our Aria brand commode. In a typical day once the tank has had material in it for 48 hours, we would get maybe 20 in a day. They land on all the food, crawl inside your wine glass, in short, it is quite a problem.
Bob, Janice & Guinness the Hound
2001 Monaco Executive (MuttRHome)
with Saturn Vue in tow
NINK is offline   Reply With Quote
Old 11-18-2017, 11:43 AM   #5
Senior Member
Join Date: Jan 2017
Location: Little Rock, Arkansas
Posts: 572
We've had those. I can't say how they get out, but they're irritating as heck! We're lucky to have a dump station on an out building with a separate well. So we flushed the tank very thoroughly after every trip for a while and seem to have them at bay.
2017 Thor A.C.E. 30.1
F53 18,000 GVWR
EdInArk is offline   Reply With Quote
Old 11-18-2017, 03:29 PM   #6
Senior Member
pointrow's Avatar
Join Date: Dec 2014
Location: Cen Il.
Posts: 432
Go to a farm store and get dairy barn spray. Fog the empty tank and anywhere else they are. Repeat till they don’t hatch out again.
That stuff is a lot stronger than what is available at the box store.


2014 Fleetwood Providence 42p
pointrow is offline   Reply With Quote

black tank, tank

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Gnats in the Black Tank or drain pipes? Dpmoore1 iRV2.com General Discussion 11 08-23-2017 10:41 AM
Gnats in black tank CWinLV iRV2.com General Discussion 3 07-11-2015 04:21 PM
Gnats flying out of the septic tank into RV DougWHolt MH-General Discussions & Problems 7 01-05-2015 12:51 AM
Help; Gnats in the black water tank D in Davie iRV2.com General Discussion 4 08-02-2012 09:42 PM
Gnats, Black Flies or No See-ums motojavaphil Just Conversation 5 07-03-2009 10:47 AM

» Virginia Campgrounds

Reviews provided by

Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 05:06 PM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.