How to Get Rid of Sewer Flies in Tempe Homes
How to get rid of sewer flies in a Tempe home: find the drain they are breeding in, scrub the slimy film out of that drain and its overflow, refill any dry traps, and keep the drain clean for a few weeks. Sprays only kill adults. The flies stop when the breeding film is gone.
- Sewer flies, also called drain flies or moth flies, breed in the slimy film that builds up inside drains, traps and overflows.
- Killing the adult flies does not end the problem. Removing the film where the larvae live does.
- Dry traps in guest baths, floor drains and laundry standpipes are a common hidden source.
- Flies that keep coming back after every drain is clean can point to a cracked pipe or a sewer line problem.
- Phoenix averages 111 days a year of 100°F or higher, so traps in rarely used drains can dry out between uses.
How to get rid of sewer flies: what should you do first?
To get rid of sewer flies fast in a Tempe home, find the one or two drains they are coming from, scrub the slime out of those drains with a stiff drain brush, flush them with hot water, and refill any traps that have gone dry.
- Find the source. Use the tape test below on every sink, tub, shower and floor drain near where you see flies.
- Scrub the drain. Push a long, stiff drain brush down the pipe and twist it to break up the slime. Do the sink overflow hole too.
- Flush. Run very hot tap water for a few minutes. Use boiling water only on metal pipes, not on plastic pipes or toilets.
- Use an enzyme or foaming drain gel if you like. These products are made to break down the organic film. Follow the label.
- Repeat. Clean the same drains every few days for two or three weeks, since eggs and larvae can survive one cleaning.
If flies still show up after that, the source may be somewhere you cannot reach. Call (480) 439-0083 to be connected with a local provider.
What are sewer flies and why are they in my house?
Sewer flies are small, fuzzy, moth-like flies that breed in the slimy buildup inside drains and sewer pipes. They show up in a Tempe home when a drain, trap or pipe has enough organic film, standing water or sewer gas for them to lay eggs.
The adults are about the size of a small gnat, gray or tan, with wings that fold like a roof over the body. The larvae live in the film of hair, soap and grease lining the drain.
How do I find which drain the sewer flies are coming from?
The easiest way to find the source of sewer flies is the tape test: put a strip of clear packing tape over each drain opening at night, sticky side down, and check it the next morning. A drain with flies stuck to the tape is a breeding spot. Test every drain, including ones you rarely use.
Check these places in order:
- Bathroom sinks and their overflow holes
- Tub and shower drains
- Kitchen sink and garbage disposal
- Laundry sinks and standpipes
- Floor drains in garages, laundry rooms or utility closets
If no drain catches flies but they keep appearing in one room, the source may be a crack in a drain line, a loose toilet seal, or wet soil under the floor.
Need help now? Call to be connected with a local provider in Tempe who can check availability for your address.
What kills sewer fly larvae in a drain?
Scrubbing is what really kills sewer fly larvae in a drain, because it strips away the slimy film they live and feed in. Hot water, enzyme drain cleaners and foaming drain gels help, but only after the film has been loosened with a brush.
A few things people try that work poorly on their own:
- Bleach. It tends to run straight past the film and down the pipe, and it should never be mixed with other cleaners.
- Bug spray. It kills the adults you can see, not the larvae in the drain.
Can a dry drain trap cause sewer flies?
Yes. A dry drain trap can cause sewer flies, because the water in the trap is what blocks sewer gas and insects from coming up out of the pipe. When a trap dries out, flies and odors can rise from the drain line below. Running water in every drain once a week keeps traps sealed.
If a trap keeps going dry even when it is used, the trap or its vent may need a closer look.
Why do sewer flies keep coming back after I clean the drains?
Sewer flies that keep coming back after you clean the drains usually mean there is a breeding spot you have not found yet, or the drain line itself has a problem. Common hidden sources are a cracked pipe under the slab, a broken sewer line, a loose toilet wax ring, or a drain with a partial clog that keeps holding dirty water.
Other signs that point past the drain opening:
- A sewer smell that comes and goes in one room
- Gurgling toilets or drains when another fixture runs
- Several drains that are slow at the same time
These are worth having checked. A local plumbing provider can run a camera into the line to see whether there is a break, a sag or buildup. Read more on the sewer line repair page or the clogged drain or sewer line guide.
How do I stop sewer flies from coming back?
To stop sewer flies from coming back in a Tempe home, keep drains clean and wet: brush out bathroom and kitchen drains every month or two, run water in every drain weekly, and fix slow drains before they hold standing water. Flies need film and moisture, so taking away both prevents new ones.
- Scrape food into the trash, not the sink, and keep grease out of the drain.
- Use a hair catcher in tubs and showers.
- Keep floor drains topped up with water.
- Have recurring slow drains cleaned before they turn into clogs. See drain cleaning in Tempe.
When should I call a plumber about sewer flies?
Call a plumber about sewer flies when they keep coming back after two or three weeks of cleaning, when you cannot find the source, or when the flies come with sewer smells, gurgling, slow drains or damp floors. Those signs suggest a pipe, trap, vent or sewer line problem that cleaning alone will not solve.
Call right away if sewage is backing up into a tub, shower or floor drain. Stop using water in the home until the line is checked. To be connected with a local provider in the Tempe area, call (480) 439-0083.
What happens during the visit?
A local plumbing provider usually starts by asking where you see the flies, what you have tried, and whether you have noticed smells or slow drains. They check the suspect drains, traps, overflows, toilet seals and vents, and may run a camera into the drain or sewer line to look for cracks, sags or buildup.
Next, they explain what they found and the options, such as cleaning a section of drain, resetting a toilet, replacing a worn trap, or repairing a damaged line. You should get a written quote before any work starts.
Why do Tempe-area homes get sewer flies?
Sewer flies can show up in any home, but East Valley conditions make a few causes more common. Phoenix averages 111 days a year of 100°F or higher (1991-2020 normals), and in that heat the water in a rarely used trap, floor drain or laundry standpipe can evaporate, leaving an open path from the drain line. The National Weather Service defines the monsoon as June 15 through September 30, and the humid storm weeks are when damp drains and backed-up lines tend to get noticed.
Hard water adds to the buildup. Mesa's 2025 report gives average hardness of about 12 grains per gallon in its City Zone and 16 in its Eastern and Southern Zones, and the City of Phoenix, which serves many homes in Ahwatukee and Arcadia, says hard water can cause scaling in pipes. The Arizona Department of Health Services also lists backed-up sewers and constant plumbing leaks among indoor moisture sources and says to remove the moisture source first.
Whether you live in Tempe, Mesa, Chandler, Gilbert or Ahwatukee, call (480) 439-0083 to be connected with a local provider who can check availability for your address. You can also see emergency plumbing help in Mesa.
Related pages
Questions people ask
Can you tell me how to get rid of sewer flies in my bathroom?
Find the drain they are coming from with the tape test, then scrub that drain and its overflow hole with a stiff drain brush and flush it with hot water. Repeat every few days for two or three weeks so new larvae cannot grow.
Are sewer flies and drain flies the same thing?
Yes. Sewer flies, drain flies and moth flies are common names for the same small, fuzzy flies that breed in the film inside drains and sewer pipes.
Are sewer flies harmful to people or pets?
Sewer flies do not bite or sting. They are mostly a nuisance, but they come from dirty drains and sewer lines, so keep them off food and counters and clean up the source.
Why do I suddenly have sewer flies in my house?
A sudden wave of sewer flies usually means a drain has built up enough slime, or a trap has gone dry, for them to breed. A new crack or slow clog in a drain line can also start it.
Does pouring boiling water down the drain kill drain flies?
Boiling water can kill some larvae, but it works much better after you scrub the drain. Only use it on metal pipes; it can soften plastic drain pipes and crack a toilet bowl.
Will bleach get rid of sewer flies?
Bleach is not a reliable fix for sewer flies. It tends to rush past the film where larvae live.
Does vinegar and baking soda kill drain flies?
Baking soda and vinegar can loosen light buildup, but on their own they rarely end a sewer fly problem. Use them along with a drain brush, not instead of one.
Can sewer flies come from the toilet?
Sewer flies rarely breed in a toilet bowl that is flushed often. They can come from around a toilet if the wax ring under it has failed and lets sewer gas and moisture leak at the base.
Why do I have sewer flies in my shower?
Shower drains collect hair and soap scum, which makes the perfect film for larvae. Pull the drain cover, clear the hair, and scrub the pipe below it.
How long does it take to get rid of sewer flies?
Most homes see far fewer flies within a week of scrubbing the right drain. Keep cleaning for two to three weeks, because eggs and larvae can survive one round.
Can a broken sewer line cause sewer flies?
Yes. A cracked or broken sewer line can let flies breed in wet soil or pipe gaps you cannot reach. If flies return after every drain is clean, have the line checked with a camera.
Can a dry floor drain let sewer flies into my garage?
Yes. When the water in a floor drain trap evaporates, flies and sewer gas can rise from the line. Pour water into floor drains regularly to keep the seal.
Do sewer flies mean I have a plumbing leak?
Not always, but they can. Flies near damp grout, baseboards or flooring with no clear drain source are worth checking for a hidden leak.
Is it safe to use chemical drain cleaner for drain flies?
Chemical drain openers are made for clogs, not flies, and they can be harsh on older pipes. A brush plus hot water or an enzyme cleaner is a gentler first step.
How do I keep sewer flies away for good?
Keep drains clean and wet. Brush out drains every month or two, run water in unused drains weekly, and fix slow drains early.
Can hot weather in Tempe dry out my drain traps?
It can, especially in drains that are rarely used. Phoenix averages 111 days a year of 100°F or higher, so run water in spare showers, sinks and floor drains every week.
What does a plumber do about sewer flies?
A plumber checks the drains, traps, vents, toilet seals and sewer line to find where the flies breed. They may run a camera into the line, then explain the options and give a written quote before any work.
Who do I call in Tempe about sewer flies that will not go away?
Call (480) 439-0083 to be connected with a local plumbing provider in the Tempe area who can look for the source and check the drain line.
Talk to someone about your plumbing problem
Call to be connected with a local provider who can check availability for your address and explain the next step.