Iron pipe sewer drain sag = sewer flies?

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.

Don2222

Minister of Fire
Feb 1, 2010
8,893
Salem NH
Hello
There are no breaks in the pipes or leaks but,
Been crazy here for 1.5 years with drain flies in the basement bathroom! At first we tried the baking soder with bleach and put so much in the kitchen drain, the PVC pipe clogged like I have never seen in my life! It took 3 days with a professional drain snake to clear the drain! Background is that most drains and water pipes in the house has been changed to PVC. The septic tank was changed to sewer by the town about 30 years ago. There is however a 10 foot section coming out of the front foundation that was the old 4” diameter cast iron and after scoping the pipe, we found a sag with standing water in it about 4 feet from the front of the foundation!!
See this $250 video!!

We also put 3/4” stone and bricks under the née PVC pipe to keep it from sagging. We also added an outside cleanout too!
Will this stop all those pesky drain flies from coming out of the clothes washer drain, the sink drain and even the toilet??
See pics below
Pic 1-2 Drain Flies!! Oh -NO
Pic 3 - sag in iron pipe going into foundation!
Pic 4 - Old iron pipe
Pic 5-7 New 4” diameter PVC pipe

B1237C38-402A-4623-B99C-B758915AA1E4.jpeg EE77893E-3F40-4E7D-90AF-1A3B2AB5DFBD.jpeg B07ABA2D-B8EC-4462-A6F7-F45DEEFABAAD.jpeg 2423F21A-D053-44C3-9048-11B58BF26896.jpeg 77A36672-5EBF-43E2-8BBA-C70FE54740A4.jpeg 031BBC7B-D0EF-467B-89E0-CF5E7E3EA0BF.jpeg 6A9F30CD-2494-4EB7-A3DE-F0BD25B9B3A1.jpeg
 
Last edited:

Don2222

Minister of Fire
Feb 1, 2010
8,893
Salem NH
jist got some of those nasty buggers coming out of the sink drain with the fruit & drain flu killer that I poured down an hour ago. :)
Maybe the pipe fix is helping??
 

Attachments

  • E8F992A9-9193-4F30-B415-198CDD7F297A.jpeg
    E8F992A9-9193-4F30-B415-198CDD7F297A.jpeg
    127.4 KB · Views: 56
  • 31837DE1-9BEB-4052-8290-EEFB71E65FC9.jpeg
    31837DE1-9BEB-4052-8290-EEFB71E65FC9.jpeg
    87.2 KB · Views: 58

heat seeker

Minister of Fire
Feb 25, 2011
3,216
Northern CT
How are the flies getting past the traps??? Unless they can swim underwater, I can't see how...
 

Highbeam

Minister of Fire
Dec 28, 2006
19,773
Mt. Rainier Foothills, WA
That green pvc is the right stuff. Sdr35 gasketed. I would have made you rip out that glue joint schedule 40.

None of that has anything to do with drain flies though.
 
  • Like
Reactions: Bad LP

EatenByLimestone

Minister of Fire
Short answer is no.

They are living off and breeding in the organic matter in the pipes. You need to get rid of the organic matter, or kill the eggs/larvae.

The quickest and easiest thing to try is to dump lots of soapy boiling water down the drain. Its hard to overwhelm the capacity of a 4" pipe though. Its not so hard on the small 1.5" drains going up to your washer, sinks, etc. Success depends on the volume you can put down them and where they are nesting.

If that does not work, you'll need an insecticidal foam. This will expand in the pipes to reach the eggs/larvae. Even if the foam doesn't reach all the way down the pipe, you can break their reproductive cycle since the flies have to crawl through the treated areas before they can fly out. Treating the areas outside the pipe with liquid residual can also help with this. The right dust should also work here.

If you can stop them from returning to lay eggs, you will solve the problem.
 

Rob711

Feeling the Heat
Oct 19, 2017
443
Long Island, ny
I never heard of, or expierenced drain flies. Always figured the traps would prevent that, once again I’ve learned from this site. I did hear the, I assumed, urban legend of the alligator coming out of the toilet!
 
  • Haha
Reactions: vinny11950

Don2222

Minister of Fire
Feb 1, 2010
8,893
Salem NH
As worms they can swim.
The drain fly life cycle is very short, I hear approx 14 days so they swim through the traps then fly out. Also there was a moldy musty type smell that was getting worse and worse. This morning is the day after the pipe fix and the smell is a lot better and only 2 flies. I know I still have to treat the drains more but atleast I did not get a dozen or so like before the fix. :)

More info on sewer line sag issues
 
Last edited:
  • Like
Reactions: Highbeam

Highbeam

Minister of Fire
Dec 28, 2006
19,773
Mt. Rainier Foothills, WA
Those dang flies can infect septic tanks too. I’ve had the worms plug up outlet filters! Gross!
 

zrock

Minister of Fire
Dec 2, 2017
1,249
bc
If your getting a smell back up through your drains then your traps are not working or are missing.
 
  • Like
Reactions: Highbeam

Don2222

Minister of Fire
Feb 1, 2010
8,893
Salem NH
If your getting a smell back up through your drains then your traps are not working or are missing.
All our drains have p traps and have water in them, that was the very first thing I checked!
I know the p traps block sewer gasses from coming back up but this is a moldy musty smell and after the sag in the line with the pool of water was fixed, the moldy musty smell went away!
More info on sewer line sag issues or bellies
 
Last edited:

zrock

Minister of Fire
Dec 2, 2017
1,249
bc
Exactly... the traps are not full enough of water or something else is allowing the smell back through... if the traps are working properly no smell will make it back into the house
 

Don2222

Minister of Fire
Feb 1, 2010
8,893
Salem NH
Check the roof vent for obstruction.
Thanks
The roof vent is all new PVC and all the drains in the house are PVC now so most of the old copper and cast iron is gone. Now that the sagged pipe is fixed, I am treating and capping all the p traps and only had 2 flies on the laundry room wall this morning. So it is getting better I hope!
Just got the grass patch in too.
Growing grass on my lawn is like trying to grow hair on a billiard ball! LOL

DD54865F-86DD-4D44-93C6-54930797DBFF.jpeg F0B126AF-3579-4620-9293-0B33A63EBCF5.jpeg 23B96169-6B95-4D5D-93A3-5E77BA36D1D1.jpeg CD5B49A1-D42C-4CB9-A676-F72F59836C5F.jpeg
 

Bad LP

Minister of Fire
Nov 28, 2014
2,001
Northern Maine
Thanks
The roof vent is all new PVC and all the drains in the house are PVC now so most of the old copper and cast iron is gone. Now that the sagged pipe is fixed, I am treating and capping all the p traps and only had 2 flies on the laundry room wall this morning. So it is getting better I hope!
Just got the grass patch in too.
Growing grass on my lawn is like trying to grow hair on a billiard ball! LOL

View attachment 280819 View attachment 280820 View attachment 280821 View attachment 280822
Ya. We have a couple of bathrooms that are rarely used for one and never on another. I was told to use mineral oil in the traps as it doesn’t evaporate but I never tried it.
 
  • Like
Reactions: Don2222

Don2222

Minister of Fire
Feb 1, 2010
8,893
Salem NH
My neighbor just have me this info on Drain Flies and where they come from!
Good stuff here!


I think I finally found the source!
I took a pic of the main house PVC drain that connects to the iron pipe in the cement floor. As you can see there are 2 drain flies, one on the wall next to the pipe and one on the pipe! So why are they this low? I crawled through the basement closet and under the front stairs to see the other side and it is damp!


1. Tighten the bands
They did need to be snugged down!
2. Clean area with Acetone
3. Sprayed one layer of Flex seal
I also have the paste for a stronger bond
Then I will fill the hole with hydraulic c

I was just thinking if the drain flies were getting into the drain pipe in the floor and then breeding in the pool where the pipe was sagging that would account for all this trouble??
Will this work??
Fingers crossed!!

05D78B4E-372F-47E0-B4A7-8E875D39A045.jpeg 4D716EFC-DFCB-49A0-AB4F-E82726FBC640.jpeg 9CFD226D-839F-48B3-B54A-294FA61B350E.jpeg 15D2C2E7-9161-44A5-86EB-AC7683AA0E04.jpeg 0D88059A-96FF-4579-9222-91845432AA8C.jpeg 230591CE-826E-4CA0-907F-4FB9E546C04A.jpeg FB4FE4A3-D95F-46B7-AFAF-654BC054348C.png
 
Last edited:

Don2222

Minister of Fire
Feb 1, 2010
8,893
Salem NH
Just saw some baby flies but definitely less and no adults. I am cutting down their food supply!
so I may take a few days!
 

Attachments

  • DA025162-AC3B-42AA-96B4-DB2068E7E82C.png
    DA025162-AC3B-42AA-96B4-DB2068E7E82C.png
    110.1 KB · Views: 44

Don2222

Minister of Fire
Feb 1, 2010
8,893
Salem NH
Well this battle is not over until there are no flies!
The spray flex seal is thin and the hole and leaky pipe seal in the hole is large. So my contractor suggested to use hydraulic cement in the hole and make it soupy! Since that got many flies out but not all, I ripped out the sheet rock and sealed the crack between the floor and wall.
Finished it all last Monday and since Monday - o Drain Flies! Ya Hoo !!!
Pic 1 - Hole where PVC pipe is connected to cast iron pipe in the cement floor
Pic 2 - Hudraulic cement from Home Depot
Pic 3 - Hydraulic cement - stopped approx 90% of the flies but not good enough!!
Pic 4 - I saw a drain fly come out from under the 2x4 on the cement floor that the sheet rock is nailed to for the wall!! Those nasty Varments!!
Pic 5,6,7 - foam Matt - if I am going to remove the sheet rock and cut out the bottom 2x4, I am not getting by butt stabbed by pointy ruff cement floor!
Pic 8 - Cut out 2x4 bottom board with sawzall to see mid tunnels and dirt brought up through the crack between the floor and the cement block outer foundation wall by nasty bugs and termites!
Pic 9 - Cleaned up debris a d wiped down with acetone to clean.
Pic 10,11 - sealed crack between floor and wall with cement sealer which contains acrylic and silicone call!
Pic 12 - Also sealed a spot where the hydraulic cement did not quite fill in!

8967B1F5-4876-412D-A1F3-732E36DEA602.jpeg 81227CA3-45D3-41C7-8EEC-08E8927EE464.jpeg E05DBEED-D1A3-43E9-BB78-7474F68E639A.jpeg 44E2C831-F313-4EA6-B937-D23D23CE8623.jpeg EFC90EA2-38D7-4263-8656-FFB0027011E0.jpeg D28C3850-50E6-46BD-8B67-78165D3EF94C.jpeg 1DF80AF6-83CA-4C07-991D-B8BA37339468.jpeg D8743FF2-9A0E-408A-A017-DD1B27076014.jpeg 12108D85-56C2-4617-BFC2-8D426C94E0C7.jpeg 91976282-351C-4241-9AB7-FA17C56D1F0A.png FB05983D-7AB4-4F04-9482-1EDD95F2E51B.jpeg 60F6BBEA-2678-4CE0-9397-074C4B5E17B5.jpeg A4FC5A2C-E274-4F0F-B1CB-6B48C3B0B68B.jpeg
 

clancey

Minister of Fire
Feb 26, 2021
2,353
Colorado
My goodness what a job you are doing and it is sad you have to handle this but you are winning and I never knew about these sewer flies and I bet they lay their eggs in the dampness where the sewer pipes are---thanks so much for updating us and those educational pictures...Your winning..clancey