Say goodbye to pesky drain flies

“Drain flies” are a common household hazard. Here’s what to do if you find some in your home.

Say goodbye to pesky drain flies

Drain flies are one of the four types of flies that can be found in Singapore. They are known by many other names including sink flies, filter flies, sewer gnats, sand flies, crane flies and filter flies. Drain flies are a type of furry, moth like fly which is attracted to stagnant pools of water. They feed on and reproduce in sewerage and other organic waste. This can cause problems for humans as drain flies are – you guessed it – prone to settling in inside sinks and other areas in the house with water drainage.

Drain flies survive off of scraps of organic material. This often means discarded food and/or sewerage will attract them and in certain conditions they could multiply to become a household nuisance. Drain flies are not technically harmful to humans. Thankfully, they are not known to spread diseases to humans and should not present active threats to the health of a household (despite their unsanitary lifestyle).

However, they can exacerbate certain conditions such as asthma or allergies. In turn, this could then lead to the contraction of some diseases such as myiasis or microfilaria. Drain flies also pose a threat to your plumbing, especially if left to multiply in significant numbers. Once they reach large numbers they can be difficult to deal with. However, drain flies very rarely get better on their own. The best advice is to act early and swiftly; the second that you suspect you may have drain flies, you should begin attempting to cleanse the house.

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There are a few strategies that you can employ when dealing with drain flies. What works best will depend on the number of flies as well as the duration that they have been living in the drain. Getting rid of drain flies is usually a simple process that you can do yourself with the appropriate information and equipment, but if you suspect that there has been damage to the plumbing you should call a professional immediately.  

Drain flies are usually easily observable and you will be able to spot them. Keep an eye out for tiny bugs on walls and ceilings, flies in bathroom or flying insects around the home. Recognising drain flies should be easy as they have a bulky, hairy body which gives them a very moth-like appearance. Drain flies are very distinct and unlikely to be confused for a fruit fly or midges. However, sometimes drain flies could be living in your pipes without you knowing or seeing them. Thankfully there is a simple test that you can do to check if drain flies are lurking inside your pluming.

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Step one

Obtain duct tape and cut a piece to the length of every drain opening in the house.

Step two

Cover each drain opening with the corresponding piece of tape. Do this at night time before bed so there is less likelihood that you will need to use any of the drains (for a shower or to wash your hands). You do not need to cover the entire drain – just a strip of tape around the center will be sufficient.  

Step three

In the morning, check the tape. If you have drain flies, there should be a few stuck to the pieces of tape. If not, this is probably good news! However, there is a chance that drain flies may be breeding in another area; if you are seeing drain flies and are convinced that they are breeding in the pipes but cannot find where, it may be time to call a professional.

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How to get rid of drain flies Singapore

Once you’ve determined that you have drain flies, terminating them is the next step. You should do this as swiftly as possible because drain flies multiply rapidly and getting rid of them will be much more difficult in large numbers.

Drain fly larvae (also known as drain worms) have a very fast hatching time of 32-48 hours after the eggs have been laid. Drain flies live about two weeks once fully grown and will be rapidly replaced by newly hatched adult flies. They can lay and hatch as many as 300 eggs in 48 hours – so you want to be very aware of the threat if it exists. Another thing to be aware of is your toilet drainage as toilets can be breeding grounds for drain flies.

Getting rid of drain flies: a step by step

There are a few methods you can try to eliminate drain flies at home without professional help. This usually involves tracking down the breeding site and clearing it completely, as the flies will die out without organic matter to feast on and live in.

You will need to clean the pipes robustly as any organic matter left behind could serve as a place for the flies to continue living. Many typical drain cleaners and home remedies will not be strong enough to completely clear the drain, which is when a professional should be called.

Option 1 – Boiling water

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Pouring boiling water down the drains will help to clear out the waste they may be feeding on. However, flies themselves are difficult to drown as they have evolutionary adaptations to help them survive in water. This method should help with a moderate number of drain flies provided they are close to the drain opening and the waste is accessible.

Option 2 – Chemical warfare (don’t worry, it’s legal)

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Another way to get rid of the stubbornly resilient drain fly population is by making the drains inhospitable. This can be done by completely destroying the organic matter in the drains. An easy way to do this is with a combination of boiling water, ntuc baking soda, white vinegar and naphthalene balls.

Pour the boiling water down the drain first, then follow up with a generous amount of baking soda. Cover the exterior of the drain pipes/outlets with baking soda as well. Scrub the sides of the pipe thoroughly. Then carefully pour a reasonable amount of white vinegar down the drain. The strong reaction between vinegar and baking soda should jolt loose any remaining grime or sludge that the flies could be feeding on. Pour more boiling water down the drain to cleanse it.

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Finally, place naphthalene balls (also known as moth balls) around the drainage outlets and cover them with a clear container. This will kill the remaining drain flies. You should keep the moth balls there for two weeks – push the container aside whenever you need to use the drain and immediately put it back. If you take the moth balls away too early, there are chances that an adult drain fly could survive to lay eggs and begin the infestation all over again.

Other options

There are many other popular strategies for killing drain flies. For example, the bug a salt product which is essentially a toy-like gun for shooting flies. This is popular because it is fun to use, and is a good way of getting rid of flies in the home. However, it will not help you to flush out drain flies at the source. This is the same with concoctions or devices that lure and trap flies. While they kill the flies that are venturing out of the drains, there are usually plenty more where they came from.

A word of advice

The best way to deal with drain flies is to avoid them altogether. There are a number of preventative strategies that can keep you from ever needing to eliminate drain flies. Regularly cleaning your drains and keeping them covered with a drain plug while not in use is one of the simplest ways to protect yourself against an infestation.


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