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How do I get rid of drain gnats permanently?

Drain gnats, also known as drain flies, are small flying insects that tend to congregate around moist areas in homes, especially in drains. They are a nuisance and can be difficult to get rid of. The good news is that with some diligent cleaning and maintenance, you can get rid of drain gnats permanently.

What are drain gnats?

Drain gnats are small flies, about 1/8 to 1/6 inches in length. They are often black or grayish in color. As their name suggests, they are commonly found hovering around drains. This is because they lay their eggs and thrive in the organic matter that accumulates in drains.

The larvae feed on bacteria, fungi, and organic matter in the slime that builds up. Drain gnats are attracted to the moist environment. They can also breed in overflow trays under houseplants.

How to identify if you have a drain gnat problem

Here are some signs that you may have drain gnats in your home:

  • Small flying insects hovering around drains or houseplants
  • Larvae in drain slime or houseplant soil
  • Adults emerging from drain openings or houseplants
  • Flying gnats that do not bite and are attracted to lights
  • Drain gnats found near decaying organic material

If you notice these pesky flies constantly buzzing around your sinks, bathtubs, or houseplants, you likely have a drain gnat infestation.

How to get rid of drain gnats

To eliminate drain gnats permanently, you need to use a combination of methods. Attacking just the adults will not be effective long-term. You need to remove breeding sites and food sources for the larvae as well.

Here are the main steps to get rid of drain gnats for good:

Remove standing water

Drain gnats need moist environments to breed. Fix any leaks or drips that allow water to collect under sinks, tubs, showers, washing machines, etc. This will remove a prime breeding area.

Clean drains thoroughly

Use boiling water to flush drains weekly. This will kill larvae and eggs. Follow up by pouring 1/2 cup baking soda down the drain, then 1 cup vinegar. Place a plunger over the drain for a tight seal. As the vinegar reacts with the baking soda, it will foam and fizz, helping dislodge gunk. Rinse drain pipes thoroughly.

Clean overflow trays

If you have houseplants, empty the overflow trays completely. Scrub away any debris or slime buildup. Repeat weekly to disrupt breeding.

Remove debris and food sources

Drain gnats feed on decaying organic matter. Remove any debris from drains by using a wire coat hanger or drain snake. Clean under sinks thoroughly, removing any food spills or residue.

Use traps

Simple DIY traps can catch adult gnats. Fill a small jar with apple cider vinegar and a drop of dish soap. The gnats are attracted to the vinegar and get stuck in the soap. You can also buy commercial sticky traps.

Apply larvicides

Applying boric acid or enzyme-based drain gel down your drains can kill off gnat larvae. These products are safe for plumbing.

Use desiccants

Sprinkle diatomaceous earth into drain openings and around houseplants. The powder will dry out and kill larvae.

Replace potting soil

Replacing old potting mix will remove any larvae from houseplants. Re-pot plants in fresh soil.

Use mosquito dunks

Add small pieces of mosquito dunks to houseplant soil or drop them into drains. They contain bacteria that kill fly larvae but are safe for plumbing.

Spray with insecticides

Insecticide sprays containing pyrethroids can kill adult gnats on contact. Spray corners, drains, and plants.

Use a dehumidifier

Running a dehumidifier can help dry out damp areas where drain gnats breed. Keep humidity below 50%.

Clean with bleach

Using bleach solutions to thoroughly clean drains, surfaces, and garbage bins helps eliminate bacteria growth.

Use sticky fly paper

Hang sticky fly paper strips near drains and plants to catch adults. This won’t kill them off completely but helps reduce populations.

Fix plumbing leaks

Repair any leaking pipes, taps, showerheads, etc. Eliminate excess moisture where gnats can breed.

Improve ventilation

Increase air circulation under sinks and in problem areas. This makes the environment less hospitable for gnats.

Use a fan near drains

Place a small fan near drains for 24/7 air circulation. The moving air makes it hard for gnats to hover.

Natural remedies for getting rid of drain gnats

If you want to avoid using chemical pesticides, there are some natural drain gnat remedies you can try:

  • Pour boiling water down drains – kills eggs and larvae
  • Salt and baking soda scrub – scrubs away organic matter
  • White vinegar – repels and kills gnats
  • Lemon juice – toxic to larva
  • Essential oils like lavender, eucalyptus, peppermint – repel gnats

How to prevent drain gnats from coming back

Prevention is key to ensuring drain gnats don’t return after eliminating an infestation. Here are some tips:

  • Clean drains weekly using boiling water or bleach
  • Use drain covers and screens to block flies
  • Keep drains dry by fixing leaks and improving ventilation
  • Remove debris and food sources where larvae can breed
  • Clean overflow trays under plants
  • Store opened food in containers or the fridge
  • Take out garbage regularly
  • Allow substrate to dry out between watering houseplants
  • Apply boric acid powder or drain gel monthly

Homemade drain gnat traps

You can make simple, effective drain gnat traps using common household items:

Apple cider vinegar trap

Fill a small jar with apple cider vinegar and add a drop of dish soap. The vinegar attracts gnats while the soap breaks the water tension, causing them to drown.

Funnel trap

Make a funnel trap by cutting a plastic bottle in half. Invert the top funnel-shaped half into the bottom half. Add an attractant like vinegar or fruit. Gnats get stuck inside.

Rotting fruit trap

Place rotten fruit like banana peels into a jar. Cover with plastic wrap and poke small holes. Fruit flies will get in but can’t escape.

Wine bottle trap

Fill a wine bottle with an inch of vinegar or wine. Roll a piece of paper into a funnel shape and put it in the mouth of the bottle. Gnats get drawn in and trapped.

Droppers trap

Fill a small dish with vinegar or wine. Position a dropper above with the bulb end facing down, over the liquid. Gnats get stuck in the bulb.

When to call a pest control professional

In most cases, you can tackle a drain gnat problem yourself using thoroughly cleaning and simple home remedies. However, if you have a severe, persistent infestation, it may be time to call in a professional exterminator. Signs it’s time to bring in backup include:

  • Drain gnats cover surfaces in bathrooms and kitchen
  • Breeding grounds are in hard to access drain pipes
  • Larvae are embedded deep in drain slime or pipes
  • Cleaning and remedies have not reduced the population after 2-3 weeks
  • You rent, so can’t make plumbing changes or modifications

A qualified exterminator has powerful commercial pesticides, equipment to clean wall voids, and tools to scrub out embedded gunk in pipes. They can find and eliminate breeding grounds and get rid of populations in walls and ceilings.


While drain gnats can be annoying, with diligence, cleaning, and persistence, you can eliminate them for good. The key is attacking not just the adult gnats but their breeding sources. Combine methods like sanitizing drains, installing traps, applying larvicides, fixing leaks, and removing food sources to get rid of populations. Then continue prevention tactics to stop those pesky flies from finding their way back!