A UV lamp is not an ordinary light bulb. One of the most misunderstood things about a UV water treatment system is why the lamp should be changed even though it still appears to be working. Why is it that the useful life is typically defined as 9,000 hours, or about one year of continual use?
The problem arises from the fact that for most of us, our understanding is heavily influenced by our experience with incandescent lights. These are your garden variety bulbs, used in most household light fixtures, it is not necessary to change or replace this bulb until it quite literally burns out.
An incandescent light bulb works by passing electricity through a tungsten filament. This generates heat that causes the tungsten to glow. That glow is the visible light spectrum, so we see the light. The tungsten filament is deteriorated with use and eventually it becomes so thin that it quite literally snaps, and no longer lights.
A UV lamp, however, operates on a different principle, more like a fluorescent light. In this case, the electricity is still passed through a tungsten filament which heats up, but that energy “excites” the mercury vapor contained in the lamp. (Not to worry, only a very small amount of mercury is used, typically