Lifting the water closet to replace the gasket allowed a dozen sewer flies to take flight! Nasty looking buggers and the homeowners groaned, “We can’t seem to get rid of those pests, and we go on a killing spree anytime we are going to have guests visit our home.”
They wanted to know how to get rid of the drain flies and produced a can of bug spray (shoot that down the drain)! While that will kill off the winged mature flies on contact, it won’t resolve the issue.
“We’ve tried pouring bleach down the drains and scalding hot water too,” said the homeowners. “Nothing seems to work.”
Bleach, hot water and pesticides will not eradicate those pesky sewer flies and playing with boiling water can do more damage than good with a real possibility for thermal scald deep-skin tissue damage.
Sewer flies don’t bite and while they do not spread diseases, however, they can contaminate foods because they carry organic decaying matter from their drain-line sites. Fortunately, they are not long distance flyers, so they tend to be near the infected drain. Left untreated, they can number in the hundreds as we recently encountered in one apartment complex.
The life cycle of a sewer fly lasts about two to three weeks and, after mating, they return to the nearby drain to lay their eggs. The eggs hatch into drain worms and feed upon the organic wastes coating the drain line. They grow to ¼-in. and hatch into adult flies within two days, so they can multiply rapidly.
Getting rid of those pesky drain flies is a seven-step process:
- Determine which drains are affected. You will typically find sewer flies nearest the drain that is their nursery. If you want to be certain that your treatment will eradicate the flies, you’ll want to treat all sink and bathtub/shower drains.
- Remove traps and tubular waste assemblies to either clean thoroughly with a drain brush, or replace the tubular goods with new product. Bag up any parts that will be discarded. Remove pop-up(s) and clean them. Remove tub plungers and trip-arm assemblies for cleaning and use the drain brush on both the shoe and overflow while also pushing it through the trap to dislodge any biofilms.
- Mechanically augur the drains.
- Water jetting is strongly recommended. Absent jetting, be sure to flush away the debris your mechanical cleaning disturbed.
- Follow this with a video inspection of the drains because a cracked or broken underground drain will provide a breeding ground you cannot treat effectively and reinfestation is likely.
- Inject a biological foaming drain cleaner to ensure the full circumference of the drain is coated. I use a turkey baster to inject the bio cleaner into lavatory and tub waste overflows. Lavatory overflow drain-tubes are often lined with the slime drain fly larva love to live in especially surrounding the pop-up assembly. Don’t forget the garbage disposal if one is present. Allow time for the bio cleaner to do its job and flush the drains again.
- As a final step, pour in drain bio gel to attack any remaining organic matter. Treat the lavatory sink and tub waste overflows too. Don’t forget the garbage disposal if one is present. Allow time for the gel to do its job and flush the drains.
Drain flies don’t have great flying skills and are fairly easy to track down to swat. A damp cloth works well for removing the splat. Bug spray works well too, but can stain and be a pain to clean off of walls and/or windows. Bug sprays should not be used in the kitchen for obvious contamination issues. An excellent alternative is dishwashing liquid. Put a few drops in a spray bottle after adding some water and swirl to mix. Spritz the flies for a clean kill!
Lavatory overflow drain-tubes are often lined with the slime drain fly larva love to live in especially surrounding the pop-up assembly.
For your homeowners (or tenants), have them boil one cup of water while mixing in one cup of sugar. After that cools, add one cup of white vinegar and a healthy squirt of dishwashing liquid. Place bowls nearby the affected drain(s) and those nocturnal sewer flies will be attracted to the odor and killed upon contact.
Drain gel treatment should be repeated after two weeks have passed just in case any pregnant adults have survived to lay eggs and then once every six months. If the underground sewer line is cracked or broken, that will need to be replaced and a recorded video inspection is a very effective sales tool.
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