Have you noticed tiny, fuzzy insects resting on your bathroom walls or hovering around the sink or shower? They may look like fruit flies or tiny moths, but they are often drain flies, also called moth flies. Their presence can be a clue that something is building up inside your plumbing.

Drain flies are small, grayish or brown insects with fuzzy wings and a moth-like appearance. They are weak fliers and commonly rest near sinks, showers, bathtubs, and floor drains. Although they are generally not considered a significant health threat, they can multiply quickly when their breeding source remains untreated.

So why are they attracted to your bathroom? Drains provide moisture, warmth, and organic material. Inside pipes, a slimy layer called biofilm can accumulate from hair, soap residue, bacteria, and other organic debris. Drain flies lay their eggs in this material, where their larvae develop.

That means killing the adult flies alone usually won’t solve the problem. Sprays may reduce the visible insects temporarily, but new adults can continue emerging from the drain. The real solution is to remove the buildup where they are breeding.

Start by thoroughly cleaning your drains with a drain brush to remove slime and debris. You can also flush drains with hot water and consider an enzyme-based drain cleaner designed to break down organic material. Follow the product instructions carefully, and avoid using boiling water if your plumbing could be damaged by high temperatures.

Next, deal with moisture. Repair leaks, clear slow drains, and prevent standing water from accumulating. Improve bathroom ventilation by using an exhaust fan or opening a window when possible. Keeping surfaces and drains as dry as practical can make the environment less attractive to these insects.

Prevention is just as important. Clean sink and shower drains regularly, remove hair and soap residue, keep floor drains maintained, and periodically flush drains with hot water. These simple habits can reduce the organic buildup that drain flies depend on.

The bottom line: those tiny flies are often a warning sign, not the main problem. If they keep returning despite thorough cleaning, there may be a hidden blockage, leak, or drainage issue. In that case, having a plumber inspect the system can help identify and eliminate the underlying source.