Drain flies: why they appear and how to get rid of them
Drain flies are actually a type of fly that resembles a moth and loves to linger around drains in your home (hence their name).
They are normally drawn to standing water, which is why you’ll often come home to them lingering in your sinks, toilets, or bathtubs after a trip away when moisture has been left to sit.
The worst thing about these pesky bugs is that they reproduce quickly. That means if you don’t deal with the issue as soon as possible, you could end up with an infestation in your hands.
Luckily, we’re here to make sure that doesn’t happen. And if it does, we provide quick and effective pest control services in and around Merseyside.
What are drain flies?
You’ll usually spot a drain fly by its tiny, fuzzy body that resembles the appearance of a moth. Besides looking so similar, they actually belong to the Psychodidae family and are a type of true fly.
Unlike fruit flies, they’re quite slow, and they thrive in standing water, which is why you’ll often see them around sinks, shower trays, baths, or even a utility room drain.
If you let your drains get to the point where a thin layer of grime has built up, you’re providing them with the perfect conditions for breeding. However, it’s not just drains they gravitate toward, it’s also anywhere in your home with longstanding moisture issues.
Drain flies can live up to two weeks, reproducing quickly in that time; they can lay up to 300 eggs every 48 hours. So if you spot them in your home, it’s time to act fast before they multiply.
Are drain flies harmful?
Drain flies are more annoying than dangerous, as they don’t bite, sting, or cause a lot of harm to homeowners.
However, they can make your home feel unpleasant and affect your everyday life. They can also pick up bacteria from drains and move it across different surfaces in your home.
One thing we do have to warn you about is using harmful products to get rid of them. Drain flies aren’t dangerous to children or pets, but the insecticides people often use to get rid of them are illegal to use since they cause health risks to humans and the environment.
What causes drain flies?
As we previously mentioned, drain flies love standing water and any undisturbed patch of organic buildup.
Dealing with a drain fly issue doesn’t mean your property is dirty; it just means there’s a moisture issue that you may not be aware of.
It’s worth noting that outdoor drains can also be the issue, especially in summer when flies are drawn to them and then fly into your home through open doors or windows.
Here are a few common causes we find when surveying people’s homes for drain flies:
Slime and build-up around drains
The most common issue: drain flies are like a moth to a flame (no pun intended) when it comes to the thin film that forms inside waste pipes, traps, and the edges of drains.
This could be a build-up of the following:
- Hair and skin cells
- Grease and food residue (especially in kitchen sinks)
- Soap scum and shampoo residue
- Bacteria and grime that collect where water doesn’t flush through properly
Unused bathrooms
When a sink or shower isn’t used for a while, water doesn’t regularly flush the pipework, creating the perfect environment for drain flies.
Any existing residue has time to thicken, and the area stays damp and still. That’s why a lot of people will come back after a short trip or holiday to find a swarm of flies around their sinks.
Standing water or slow drainage
Anywhere water sits or moves slowly is more likely to develop the build-up of grime or slimy film that drain flies gravitate towards.
This means:
- Partially blocked pipes (hair, grease, limescale)
- Water sitting in a floor drain or gully
- A sluggish shower drain that never fully clears
- A trap that holds stagnant water because the drain is rarely used
Hidden leaks and damp
You can’t always spot every small leak or damp build-up in your home. So if you can’t identify any obvious causes, this is most likely the case.
Look for:
- A leaking shower waste underneath the tray
- A slow drip under the sink or around the trap fittings
- Damp patches under the flooring near a bathroom or kitchen
- Faulty pipework behind a washing machine or dishwasher
A step-by-step guide to getting rid of drain flies
If you’ve tried a standard fly spray and they keep returning, you’re not doing anything wrong.
Sprays may reduce them for a short while, but they don’t remove the place where the larvae are growing. The good news is that drain flies are usually straightforward to deal with once you focus on the source.
Here’s how to do so:
1. Find the source
Search for any areas that could be attracting drain flies to your home, whether it’s a grimy, clogged drain, a leak, or standing water.
To test it out, place some clear, sticky tape on the potential source and check whether any drain flies are stuck to the tape after a day or so.
2. Scrub any drains
If the drains are the issue, use a drain brush (or an old bottle brush) to scrub the inside lip of the drain and as far down as you can safely reach.
Remove and clean the waste cover and any hair catcher when scrubbing showers or bathtubs. Make it a habit to scrub them regularly to prevent build-up.
3. Flush with hot water after cleaning
Once you’ve given your drains a good scrub, pour hot water down the drain to break down and wash away any remaining debris.
It’s best to avoid boiling water, as this can damage pipework (such as PVC pipes).
4. Use a biological drain treatment
Biological drain treatments are effective at preventing drain flies from returning.
Microbial/enzymatic drain treatments are designed to break down the organic material that lines pipes, removing the main food source that keeps drain flies returning.
5. Use baking soda and vinegar (alternative treatment)
If you can’t get your hands on any biological drain treatment, baking soda and vinegar also work a treat.
Just mix half a cup of baking soda with half a cup of salt, then pour it down the affected drain, followed by half a cup of vinegar. Let it sit for a few hours, then wash out the drain with hot water.
6. Remove food and water sources
Slow drains, blockages, and leaks will keep on inviting the drain flies back, even if you address every other cause.
The best thing to do is clear out any hair or grime blocking your shower drains and the trap under the sink, if you can do so safely.
You should also address any leaks or damp spots, such as holes around showers or bathtubs, toilet bases, and under-sink pipe joints.
When it’s time to call Premier Pest Control
If you’ve scrubbed, treated, and checked for leaks, but you’re still seeing drain flies after 10–14 days, the source may be deeper in the pipework, coming from a floor drain or external gully you’ve missed or a leak you can’t see.
Our experts have dealt with this issue many times and will identify the source on one visit. We’ll then provide a quick, effective pest removal plan to keep your home free of drain flies.
Give us a call today to get rid of pest issues once and for all.