The UV Light Is On. Is It Working?
A glowing UV bulb can be a dead UV bulb. Why the light lies to you, and the two things that actually decide whether your water is being disinfected.
By Danny Lachhman · Owner, 360WATER Systems Inc. · Orangeville, Ontario
This is the most dangerous piece of false comfort in water treatment: walking past the UV system, seeing the bulb lit, and assuming the water is safe.
A UV lamp’s disinfecting output fades with hours of use — even while it still glows a perfectly healthy-looking blue. That’s why UV lamps are rated for about a year of continuous service (roughly 9,000 hours) and why better systems count down the days and alarm when the lamp is due. Past that point you have a night-light, not a disinfectant. The rule is simple: replace the lamp every 12 months, lit or not.
The second deciding factor is the quartz sleeve the lamp sits in. On well water, hardness and iron film build up on that sleeve, and UV can’t get through a dirty sleeve no matter how new the lamp is. The sleeve needs to be cleaned — or replaced if it’s etched — when the lamp is changed.
Two more honest points about UV:
- It disinfects at one point, and leaves nothing behind. UV adds no chemical and leaves no residual protection. Water contaminated after the UV — a cracked line, a dirty storage tank — stays contaminated. It’s an excellent barrier, not a force field.
- It does nothing while the power is out. No electricity, no disinfection. On a well, that’s worth remembering during outages, along with the usual boil-water caution after pressure loss or flooding.
Keep up the lamp-and-sleeve routine and a UV system is one of the most reliable tools there is. Just don’t let a glowing bulb do the talking.
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