How to Deal With Drain Flies in Your Bathroom and Kitchen

October 8, 2026

What Are Drain Flies?

Drain flies (also called moth flies or sewer gnats) are tiny, fuzzy-winged insects that breed in the organic slime buildup inside pipes and drains. Unlike fruit flies, they don't care about food — they live in the drain itself, which is why surface traps alone rarely solve the problem.

How to Confirm It’s Drain Flies

Place a piece of tape sticky-side-down over the drain opening overnight. If small fuzzy flies are stuck to the tape in the morning, you have a drain fly infestation. Their wings are distinctly rounded and moth-like, unlike the elongated wings of fruit flies.

Step 1: Clean the Drain Buildup

Drain flies need the organic biofilm inside your pipe to breed. Pour boiling water down the drain twice a day for several days, then scrub the drain interior with a long-handled brush and dish soap. Remove the drain cap and clean underneath it too.

Step 2: Use Fly Strips to Catch Adults

While you're treating the drain, capture adult flies to reduce the population. Hang Sulguy Fly Strip Glue Traps near affected drains. They're chemical-free and capture flies on contact without any spray or smell.

Step 3: Add a Peppermint Repellent Layer

After cleaning, spray around the drain opening, under the sink cabinet, and nearby walls with Sulguy Peppermint Bug Spray. The scent deters flies from returning to the area while you complete the drain treatment cycle.

Step 4: Treat Stubborn Drains With Crawling Pest Powder

For drains that remain infested after cleaning, apply Sulguy Crawling Pest Control Powder Spray into the drain opening. The dry formula reaches into crevices and coats surfaces where biofilm accumulates, disrupting the breeding site at its source.

Glue Traps on the Floor for Ground-Level Monitoring

Lay Sulguy Insect Glue Traps flat on the bathroom floor near the drain. Drain flies tend to rest on cool surfaces at night, and flat traps catch them more effectively than hanging strips in low-ventilation bathrooms.

Prevent Recurrence: Keep Drains Moving

Drain flies thrive in slow or stagnant drains. Run hot water for 30 seconds after every use, use a drain hair catcher to reduce buildup, and clean drains monthly. Bathrooms that go unused for weeks are especially vulnerable.

Eliminate Bathroom Odors After Treatment

Once the infestation clears, the bathroom may retain musty odors from the biofilm. Place a Sulguy Bamboo Charcoal Bag in the bathroom to absorb moisture and odor naturally — no synthetic fragrance needed.

Also Check These Hidden Spots

Drain flies can breed in overflow drains (the hole near the top of your sink), condensation trays under refrigerators, and washing machine drain hoses. Check all of these if flies persist after treating the main drain. More hidden breeding spots are covered in our Hidden Pest Breeding Spots guide.

UV Trap as a Supplementary Catcher

In bathrooms or kitchens with persistent fly pressure, run a Sulguy UV Mosquito Trap overnight. UV light attracts drain flies and other small flying insects, capturing them passively while you sleep.