How to Get Rid of Drain Flies Forever

A single drain fly can lay up to 200 eggs that hatch within just 48 hours.

These tiny, moth-like creatures might seem harmless at first glance, but their presence is a clear indicator that there may be problems with your drains.

The good news is that proven methods exist to eliminate them. Following simple weekly cleaning routines and professional solutions will help you get rid of drain flies and stop them from coming back.

Understanding Drain Flies

Drain flies, also called sink flies, filter flies, sewer flies or sewer gnats, are members of the Psychodidae family.

These pests resemble moths more than flies and can be distinguished by their fuzzy, hairy bodies and wings covered in fine scales. Their bodies measure 1.5 to 5mm in length and can be light grey or black in colour with pale wings. When swatted, these flies leave a dusty mark behind.

Drain flies behave differently from other household pests. They don’t fly very well and tend to make short, hopping movements when disturbed. This explains why people usually see them crawling on bathroom walls instead of flying around. You’ll often spot them resting on vertical surfaces near drain openings during the day. They become much more active as night falls.

The drain fly’s lifecycle accelerates their population growth. Each female can lay anywhere between 30 to 200  eggs per batch in the organic material that collects inside wet drains. The eggs take just 48 hours to hatch into almost see-through larvae that eat the decaying organic matter. The entire journey from egg to adult takes 8 to 24 days, depending on the environment.

These flies persist stubbornly because of their preferred living spaces. The slimy organic film inside drains, sewers and pipes creates the perfect home for them and is difficult to remove. Their larvae show impressive toughness and can survive with little oxygen and extreme temperature changes.

People often mix up drain flies with fruit flies, but they’re quite different. Fruit flies love rotting fruits and vegetables, while drain flies specifically choose the decaying matter in drains and sewers. The easiest way to tell them apart is by looking at their appearance.

How to Identify a Drain Fly Infestation

Small, fuzzy insects on your bathroom walls could be the first sign of drain flies. These pests rest on vertical surfaces near drains during the day. Their numbers start small but grow steadily as the problem worsens.

These distinctive features will help you identify drain flies:

• Small insects (1.5mm to 5mm) that look like miniature moths
• Grey to black bodies with light coloured wings
• A weak, erratic flight pattern with short hops
• They become more active in the evening
• You’ll find them resting on walls and ceilings during the day
• They leave a powdery residue when crushed

The tape test should give you solid proof of an infestation. Cover half of the suspected drain opening with clear adhesive tape (sticky side down) overnight. Drain flies emerging from that drain will stick to the tape by morning. Another option uses a clear plastic cup coated with a thin film of vegetable oil, placed upside down over the drain overnight.

Discovering larvae gives conclusive evidence beyond adult flies. These worm-like creatures (4mm to 5mm long) look translucent or greyish with darker heads. You can spot them wriggling in the slimy lining inside drains. They show up clearly in rarely-used toilets and drains where water sits for a week or more.

The number of adult flies you see each day shows how bad the problem is: 1 to 5 flies points to a mild problem, 6 to 20 means a moderate infestation needing quick action, while more than 20 flies signals a severe case that might need professional help.

It’s worth mentioning that if you notice drain flies coming back quickly after basic cleaning, then breeding has taken root in your pipes. This will require more thorough treatment.

DIY Methods to Eliminate Drain Flies

To get rid of drain flies, you will need to follow specific methods that break their breeding cycle. A few DIY solutions can help you take back control of your drains without professional help.

Boiling Water Treatment

A simple first step to fight drain flies is pouring boiling water straight down affected drains. You’ll need to bring a medium-sized pot of water to a rolling boil and carefully pour it down the drain opening. The best results come from doing this 1 to 2 times per day for about a week. Be careful with PVC pipes since water at 100°C can potentially damage them. This method works by removing organic matter and kills larvae near the drain opening.

Natural Enzyme Cleaners

Enzyme-based drain cleaners are a great alternative to harsh chemicals. These cleaners use special bacteria that eat away the organic matter drain flies need for food. In Australia, you can find commercial products like Drain Clean with microbial formulas that break down grease, fats, hair and other organic materials that attract drain flies. Just follow the product’s instructions. They usually recommend that you apply it at night when drains aren’t used much. Most enzyme cleaners work best with weekly applications after the original treatment.

Vinegar, Baking Soda and Salt Solution

Mix these ingredients for a powerful cleaning solution:

• Half a cup of salt
• Half a cup of baking soda
• One cup of white vinegar

Pour the mixture down your affected drain, plug it and let it sit overnight. Flush it with boiling water in the morning. The chemical reaction helps kill larvae and breaks down organic buildup. You’ll see the best results using this method regularly over several days.

Manual Drain Cleaning

Physically removing drain gunk is one of the quickest ways to solve the problem. Clean your sink with a regular cleaning solution first. A pipe brush or drain snake helps scrub inside the drain and removes hair, slime and organic debris. These tools can reach up to three feet inside drains. Hot water flushing will remove any loosened material after mechanical cleaning.

When to Call a Professional Plumber

Unfortunately, these fuzzy pests might keep coming back even after your best DIY efforts. This could mean you have deeper plumbing issues that need professional help. If they return after multiple treatments, you should think about calling a licensed plumber.

Licensed plumbers know exactly how to find and fix drain fly problems at their source. They have specialised tools to open pipes, find breeding spots and clean blockages that homeowners can’t reach. A plumber can also spot hidden issues like cracked pipes, sewer line problems or poor drainage that create perfect breeding grounds for drain flies.

Call a professional plumber if:

• Your DIY treatments haven’t reduced drain flies after two weeks
• You see drain flies in multiple drains across your home
• There are sewage smells along with the drain fly problem
• Drain flies come back quickly after treatments seem to work
• You spot more than 20 adult flies each day

Professional plumbers don’t just kill drain flies—they find and fix the underlying problems. They can repair damaged sewer pipes, remove contaminated soil clogs and fix leaking pipes that create moisture in walls or under floors. This approach tackles both the drain flies and the plumbing issues causing them.

If you want to get rid of drain flies or require expert plumbing services, Parker Plumbing is ready to help. Our team of licensed professionals have been servicing Ipswich and Brisbane for over 15 years. Call us at 07 3177 2019 to book an appointment.

Dan Parker

Dan Parker is the Director of Parker Plumbing and has over 16+ years of experience in the plumbing industry. His commitment to providing exceptional customer service means that he has seen it all – anything to do with residential or commercial plumbing, he knows what to do. Passionate about helping people in his community, Dan strives to offer honest and reliable plumbing services in the Brisbane and Ipswich areas.