The key difference between UV and UVC is the wavelength. UVC has a very short wavelength of 100-280 nanometres (nm), whereas UV is a lot longer. Ultraviolet light can range up to 400 nm. UVC lamps are designed to emit the right amount of radiation to effectively sterilise water.

You’ll want a lamp that emits a wavelength of 260-265nm, as this is the most effective at damaging DNA in microorganisms, which is the aim of UV water treatment. If you choose a lamp UVC over UV light, you can remove 99% of microbes from any water you’d like to sterilise.