Next to the filter elements in water systems that need replacement is the UV lamps replacement. Generally UV lamps require replacement annually. This is because they degrade. At the start of their life when they are new UV lamps (depending on quality) emit UV intensity of around 100%. As they get older this intensity reduces to the point where the water passing through the UV chamber is not getting enough exposure to sterilise any bacteria that may be present in the water.
The manufacturers of these UV lamps generally recommend an annual replacement. It is of course fair to say that these companies have a vested interest in making you replace UV lamps more frequently than is required. However there is a fair bit of math in the formula that governs whether your water system works correctly. In simple terms the formula is based on water tepidity (clarity), water flow through the chamber, the chamber length and width and the lamp wattage.
Therefore if the lamp wattage is compromised or has diminished then so is water exposure time. So our testing as an average indicates that most UV lamps will last for up to 18 months but not much longer. At the end of this period they may well still be illuminating but they will not be emitting the level of UV light to do the job correctly. So with an average price of a UV lamp from us at $100 plus tax it is advisable to do an annual lamp replacement or at worse case every 18 months.