Ultraviolet systems fail by neglect rather than by breaking, and the neglect is easy because nothing about the water changes when they stop working. A short maintenance calendar removes the guesswork, and it has only a handful of entries, one of which most owners have never been told about.
Annually: the lamp and the sleeve
Replace the lamp whether or not it still glows, because germicidal output fades long before the visible light does and a glowing lamp is not evidence of treatment. Clean the quartz sleeve at the same visit, since a film of iron, manganese or scale cuts the delivered dose exactly as a worn lamp does. Replace the sleeve o-ring while everything is apart. Clean the intensity sensor window if the unit has one, because it fouls from the same water and drifts as a result.
Quarterly: the pretreatment and the sleeve's condition
Check and change the sediment cartridge and any other filtration ahead of the chamber, since the lamp inherits whatever those deliver. While you are there, look at the sleeve if it is accessible: a sleeve that films visibly between annual services is telling you the pretreatment is not keeping up, which is a specification problem rather than a maintenance one and worth acting on before another year passes.
After any interruption
This is the entry most owners have never been given. After a power cut, a lamp failure, a period when the property was empty, or any work on the plumbing, the water in the system and the pipework downstream has been standing without treatment or has passed the chamber untreated. Let the lamp reach full output, then flush every tap for several minutes before drinking, and consider bottled water for the first day after a long absence.
Periodically: test the water
The EPA notes that private wells are not federally regulated under the Safe Drinking Water Act, so nobody samples on your behalf, and an ultraviolet system produces no evidence of its own success. A test after commissioning and periodically afterwards is the only confirmation available, and it is what closes the loop between equipment that appears to run and water that is actually being treated. Our uv bulb guide covers sourcing lamps and sleeve o-rings by model.
Questions people ask about uv light water filtration
What has to be done annually?
Replace the lamp regardless of appearance, clean the quartz sleeve and the sensor window, and fit a new sleeve o-ring.
How often should pretreatment filters be checked?
Quarterly is a reasonable habit, since the lamp inherits whatever the filters deliver and a filming sleeve means they are not keeping up.
What should I do after a power cut?
Let the lamp reach full output, then flush every tap for several minutes before drinking, since standing water was untreated.
Do I still need to test the water?
Yes. The system produces no evidence of its own success, so a periodic test is the only confirmation it is working.