How to Get Rid of Drain Flies

Confirm you have drain flies

Before you treat anything, make sure you are really dealing with drain flies. Adults measure 2–5 mm (up to about 0.20 in) and are usually gray and black. Look for these features:

• Fuzzy, gray, leaf-shaped wings held roof-like over the body
• Short, weak, hopping flight
• Found near drains, especially in bathrooms

They are most often confused with fruit fly and fungus gnat. See the full drain fly profile for side-by-side details.

Why you have drain flies

Drain Flies come indoors looking for food, water, warmth or shelter. Gaps around doors, windows, pipes and utility lines give them easy ways in. Clutter, leaks and food left out let a small problem grow into an infestation. They are most active in spring, summer, fall and winter, so expect to see more of them then.

When you'll see drain flies

Drain Flies are most active in spring, summer, fall and winter. In spring, overwintering adults become active and many species lay their first eggs. Summer heat speeds up development, so populations can grow quickly. In fall, many bugs look for shelter, and some move toward or into buildings. In winter, activity continues mainly indoors in heated spaces.

Typical places to check: bathroom, kitchen and basement or garage.

Step-by-step: getting rid of drain flies

Step 1: Scrub drains with a stiff brush to remove the organic film

Scrub drains with a stiff brush to remove the organic film. Repeat this for at least two to three weeks, since eggs and hidden insects keep appearing for a while.

Step 2: Pour boiling water or an enzyme drain cleaner down slow drains

Pour boiling water or an enzyme drain cleaner down slow drains. Keep notes on where you still see activity so you can focus your effort.

Step 3: Fix leaks

Fix leaks and dry out damp areas. Keep notes on where you still see activity so you can focus your effort.

Natural and low-toxicity options

These methods work well alongside the steps above and keep chemical use to a minimum:

• Vacuum insects and egg cases, then empty the canister outdoors right away.
• Wipe surfaces with soapy water to remove scent trails and residue.
• Place sticky traps to find out where activity is highest.
• Run a dehumidifier where damp areas attract them.

If you do use a pesticide, choose one labeled for this pest and the place you're treating, and follow the label exactly. The label is the law.

When to call a professional

Call a licensed pest control company if you still see drain flies after three to four weeks of steady effort, if they are spreading to several rooms, or if you share walls with neighbors who have the same problem.

How to keep drain flies from coming back

• Seal cracks and gaps with caulk and install door sweeps.
• Store food in sealed containers and take out trash often.
• Fix leaky pipes and faucets and keep basements dry.
• Trim shrubs and branches so they don't touch the house.
• Keep firewood, mulch and debris away from the foundation.

Safety notes

Drain flies don't bite and aren't known to spread disease in homes.

Keep children and pets away from any traps, baits or treated areas.

About flies & mosquitoes

The drain fly is one of the flies & mosquitoes. Flies have only one pair of working wings; the second pair is reduced to small balancing knobs called halteres. They go through complete metamorphosis, and the larvae, called maggots, need moist organic material such as garbage, soil, drain film or standing water.

Fly problems are almost always breeding-site problems. Finding and removing the moist material where larvae develop works far better than swatting adults.

Frequently asked questions