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
Do you have a trap on the clothes washer line? If not, can close the gap around the drain hose where it goes into the wall box? A piece of foam pipe insulation to fill around the gap. I've seen drain flies appear when traps dry out. If not a frequently used bathroom, run water maybe once a week to fill traps.
This ^ ^ ^ That sag in the main line can cause other problems, but should not cause sewer flies, because there will be daily flow through there (if that is indeed the main sewer lateral to the street) and all drain connections should have a trap on them...and yes, it is common for people to forget about basement drains back in some dark corner, or drains that were covered up when the house was remodeled/basement finished...then those drain traps can dry out and cause sewer gas issues, flies, etc. Stagnant water can be an issue too. Those pesky little buggers won't come out through a filled trap (the adults...the larva can live in the trap though...that's why they need to have water drained through pretty often) but they can be hard to get rid of once you have them in the house (they are just seasonal though) one thing you can try is they stick to those sticky fly strips pretty well so... 4 Amazingly Simply Ways to Get Rid of Drain Gnats
Yes, all drains have P traps including the washer drain. We do use them frequently that is why I was so baffled.
Those flies were coming thru all the p traps and even the toilet and filled the sticky fly papers we hung up! When we came back after a few days of vacation the fly papers were loaded with those nasty buggers!! No other issues with the pipes except that sag! No breaks no leaks, nothing!!
We also see the drain flies occasionally, but only in bathrooms or showers/ tub that never get used. Running water to fill the trap fixes it. Not sure how they are getting thru full traps. Gonna go run some water now!
The adult flies might hang around those areas, but they are not coming out of a full trap that is used regularly...there has to be another source...maybe a sump crock...or a wet area around the foundation? No possibility of a hidden drain buried in a wall somewhere...or, another thing I have heard of is a vent stack that was rotted out...easy access for the flies there...should be a smell associated with that one though.
The old copper vent stack for the toilets were replaced with PVC all the way up through the roof a few years ago. I have seen with my own eyes those flies coming out of the sink drain, washer drain and toilet just before using it!! Just 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??
That's what I'm saying though, yeah they like to hang out in there, but that doesn't necessarily mean that's where they came from...its almost impossible if the drain is used regularly, because the larva gets washed down the line past the trap, and once hatched I'm pretty sure the adults can't swim through a full trap back into your home. I don't think most of the stuff you pour down the drain kills the adults, just the larva...and the adults live something like 3-4 weeks, so you have to keep up whatever preventative measures you are using on your drains long enough to break their life cycle and be done with them, for the year anyways. Use THIS to Quickly Get Rid of Drain Flies (Amazing All Natural Trick) This link describes an interesting drain cover/trap too...
Was that a mis-type? Normally people use baking soda with vinegar to clear/deodorize drains as well as use it as a mildew-cide (bleach does not kill mold/mildew all the way thru). The chemical reaction helps any stuck goop loosen up and drain. I'm not sure there is a chemical reaction between baking soda and bleach, although supposedly they do work well together in whitening clothes / removing stains in fabric.
I tried a lot of baking soda and vinegar but it harden and blocked up the drain like I have never seen in my life! I had to purchase an industrial drain snake and it took 3 evenings to free up the blockage from the kitchen sink! I am done with that! The fruit fly killer for $12 at Home Depot works better than anything else I have tried! Also the morning after the pipe fix, that horrible moldy mildew smell is completely gone so fixing the sagging pipe filled with dirty water did something!
More info on sagging sewer line Sewer Line Belly 101 – Causes, Proper Identification, and Repair | Pipe Spy Blog | Oakland/East Bay
Something is not sealed up somewhere then...everything should be water/gas tight past the traps...no smell from the lateral should be able to get out...
We do have a p trap on the washer drain, it was put in new a few years ago but even the old one had a p trap too! I am also looking into the Fernco washer drain connectors like this one to seal the trap and our Lowes did not have any in stock, but really do not think it will help. :-( Fernco 2-in x 1.89-in dia Flexible Donut PVC Fitting in the PVC Fittings department at Lowes.com Good Idea on the piece of foam, like a piece of pipe insulation! Thanks
I just found a piece of pipe foam insulation from Home Depot with a 1” inside diameter that blocks the washer drain perfectly.
Hi I just found something? Where the main drain goes into the basement floor, there is a drain fly?? The front side of this 4” pipe looks pretty good but look at the back side!! What is going on? Looks damp? How can it be fixed?
