Bathroom UV Lights: What You Should Know?

Written By Adam Paul - Waterproofing Expert

UV light is used in the bathroom to disinfect, sanitize, and control mold and bacteria growth in bathroom damp corners, grout lines, and undersink cabinets where moisture lingers and is hard to clean.

UV light can kill bathroom mold. UV-C light consists of 100 to 280 nm wavelengths, and it effectively penetrates into the mold spores and destroys the DNA structure of the mold. This process kills the molds and stops the spreading of mold in the bathroom as colonies.

UV light can kill all the mold types in the bathroom, commonly grow on the bathroom walls, sink areas, shower, and toilet areas. UV light will take 10-15 minutes to kill the mold in the bathroom. The killing rate depends on the intensity of the UV lamp, the distance from the mold, and the duration of exposure.

You should place the UV light near the moisture-prone areas without posing a direct exposure risk to humans. UV light is harmful to humans. When the UV light is on, the bathroom should not be used to prevent skin burns, eye injuries, and long-term tissue damage. To prevent this, UV-C damage devices have built-in safety features like motion sensors, timers, remote control, or shielded or enclosed UV-C fixtures.

Why is UV Light Used in the Bathroom?

UV light systems are highly recommended in poorly ventilated, high-moisture, and lower sunlight bathrooms. It helps to prevent secondary water damage, such as mold behind drywall, peeling paint, or seepage due to microbial deterioration.

Can UV Light Kill the Mold?

Yes, UV light can kill the mold. UV light consists of UV-C light, which operates in the 200-280 nm wavelength range. It destroys the DNA and RNA of microorganisms like E. coli, mold spores, fungi, and viruses in the bathroom area and prevents them from reproducing.

How Does UV Light Kill Bathroom Mold?

UV light kills bathroom mold by effectively destroying the DNA of mold spores. It prevents the mold from growing and spreading over the organic materials.

When mold is exposed to UV-C light, the high-energy beams penetrate the cell walls of mold spores. It causes mutations or completely destroys the mold DNA. As a result of this, mold spores are destroyed before they can colonize the organic surfaces in the bathroom.

What Mold Types Kill by UV Light in the Bathroom?

UV-C light can kill various types of mold in the bathrooms, such as black mold (Stachybotrys chartarum), Aspergillus, Penicillium, and Cladosporium.

These mold types commonly grow on the bathroom walls, sink areas, shower, and toilet areas, which have higher moisture content in the bathroom.

How Long Does it Take to Kill the Mold in the Bathroom?

UV light will take 10-15 minutes to kill the mold in the bathroom. The killing rate depends on the intensity of the UV lamp, the distance from the mold, and the duration of exposure. UV light can kill mold in several minutes when it is directly exposed to the UV beams. But a deeper or more embedded mold will take longer exposure to UV light.

UV-C light is most effective in killing mold on surfaces that are directly exposed to the rays. This includes areas like the bathroom shower, bathtub, sink, tiles, and other flat surfaces where mold and mildew commonly grow in the bathroom.

Where Should UV Light be Placed in the Bathroom?

UV light should be placed in the bathroom where it can effectively sanitize moisture-prone areas without posing a direct exposure risk to humans. Aqviz experts always recommend you to place the UV lights in these 5 areas to kill the mold effectively and protect humans.

Ceiling-mounted fixtures
Inside exhaust ventilation systems
Under sink cabinets,
Behind mirrors or vanities
Near floor drains or shower corners.

UV light may not be as effective in killing mold in areas that are shaded, blocked, or porous in the bathroom. Because UV light does not penetrate materials like wood or dry walls, which harbor materials for the molds. Hence, molds which are behind walls, under tiles, or deep within grout lines may not be completely killed because it is not exposed to UV rays.

How Long Should UV Light Stay On in the Bathroom?

UV-C light should stay on in the bathroom for 15 to 60 minutes per cycle , depending on the size of the space, the intensity of the lamp, and the type of contaminants targeted.

For small residential bathrooms , a 15-30 minute UV-C cycle once or twice daily is usually enough to reduce bacteria, viruses, and mold spores on exposed surfaces.

In commercial or high-traffic bathrooms , longer exposure, up to 60 minutes , may be required for deep sanitation, particularly around floor drains, urinals, and under-sink areas.

Is it Harmful to Use the Bathroom with UV Light On?

Yes, it is harmful to use the bathroom while UV-C light is on. UV-C light can damage skin and eyes, so the bathroom should be vacant during operation. When you are exposed to UV-C light, you can observe below symptoms.

Skin burns (UV dermatitis)
Eye injuries (photokeratitis or “welder’s flash”)
Long-term tissue damage with repeated exposure

That’s why Aqviz experts always recommend using UV-C devices with built-in safety features such as:

Motion sensors that shut off when someone enters the room
Timers that automatically power off after disinfection
Remote control or app-based operation
Shielded or enclosed UV-C fixtures (especially for HVAC-integrated or under-sink units)

What is UV Light?

Ultraviolet (UV) light is a type of electromagnetic radiation with a wavelength shorter than visible light but longer than X-rays. The wavelength of UV light is 100 to 400 nanometers (nm) and is classified into three types: UVA, UVB, and UVC. UVC light. UV-C light consists of 100 to 280 nm wavelengths and it is mostly effective in mold killing.

How do I know if there is UV Light in the Bathroom?

If there is UV light in the bathroom, you can determine it by following 4 ways.

Visible bulb or fixture : Some UV-C lights emit a bluish or violet glow, but not all are visible to the human eye. If you see a glowing tube or lamp labeled for sterilization, it’s likely UV-C.
Labels and markings : Look for markings like “UV-C,” “germicidal,” “254 nm,” or “disinfection lamp” on the fixture, bulb, or control panel.
Control panel or timer switch : Many UV-C lights are installed with dedicated switches, timers, or motion-sensor controls to manage operation while ensuring safety.
Manufacturer’s information : Check the model number or brand near the light fixture. A quick search on the manufacturer’s website can confirm if the device emits UV-C.

But you should know that you can’t identify the UV light using a standard mobile phone camera or using any app.

How to Prevent Mold Growth in the Bathroom?

These 5 ways help to prevent mold growth . Preventing mold growth is always better than killing mold.

Waterproof bathroom surface: You should waterproof bathroom surfaces such as walls, and floors to prevent water leaks and seepage to the materials. When answering the question How to waterproof a bathroom , you should install a waterproofing membrane on both bathroom walls and floors. You can install liquid waterproofing and sheet waterproofing membranes in the bathroom.
Improve ventilation in the bathroom: Bathroom ventilation can be improved by installing a bathroom exhaust fan, and using it during and after showers helps to remove excess moisture from the air. As well as open doors and windows as much as possible to receive more air from the outside.
Use a dehumidifier in the bathroom: Dehumidifiers remove excess moisture from the air in the bathroom. It makes the environment drier and it prevents mold and mildew growth on the organic matter.
Fix leaks in the bathroom: Any water leaks from the faucet, showerhead, or plumbing under the sink can create a damp environment where mold can thrive. Fixing leaks in the environment can control the bathroom humidity and prevent mold growth
Keep surfaces dry in the bathroom: Keep bathroom surfaces dry, which helps to stop mold and mildew growth in the bathroom