Replacing the lamp is the one piece of maintenance an ultraviolet system genuinely demands, and it is straightforward once a year provided the right lamp is on the shelf when the reminder comes. Getting it right means matching the lamp to the chamber rather than to a wattage figure, and handling the new one carefully enough that it lasts its full term.
Match the lamp to the system, not the wattage
Germicidal lamps are specified by length, base and pin configuration, and electrical characteristics, and two lamps of the same nominal wattage can be entirely different parts. Take the model number from the system's label or from the old lamp's own printing, and order against that rather than against a description. Getting it wrong is not usually dangerous, since a mismatched lamp will not seat or will not strike, but it is a wasted week without treatment. Keep the model number written somewhere that is not the lamp itself.
Handling the new lamp
Do not touch the glass. Oils from skin leave marks that etch when the lamp is running hot and create local hot spots that shorten its life, which is why lamps arrive in a sleeve and why gloves or a clean cloth are worth using. Slide it into the quartz sleeve rather than forcing it, seat the connector fully, and take the opportunity to inspect and clean the sleeve at the same time. Replace the sleeve o-ring while everything is apart, since it is the seal holding water out of the lamp chamber.
Doing it safely
Isolate the power before opening anything, and do not look at a lit germicidal lamp: the wavelength that inactivates organisms also damages eyes and skin, and there is no warning sensation at the time. Depressurise and isolate the water side before removing the sleeve, since the sleeve is under line pressure in service. Let a lamp cool before handling it. Lamps contain a small amount of mercury, so the old one should go to an appropriate collection point rather than into household waste, and a broken lamp needs careful cleanup.
Why annual replacement is not negotiable
Output declines steadily through a lamp's life and passes below the useful dose well before the lamp stops emitting visible light, so a glowing lamp is not evidence of treatment. The EPA notes that private wells are not federally regulated under the Safe Drinking Water Act, so nobody is checking your water but you, and a lamp left in for two years is a system that has been reassuring rather than treating for months. Note the date on the housing at every change. Our uv bulb guide covers sourcing lamps and sleeve o-rings for the common systems.
Questions people ask about uv lamp water treatment
How do I find the right replacement lamp?
Match the system model number or the printing on the old lamp. Length, base and electrical characteristics all have to match, not just the wattage.
Why should I not touch the glass?
Skin oils etch the quartz when the lamp runs hot, creating hot spots that shorten its life. Use gloves or a clean cloth to handle it.
Is it dangerous to look at a UV lamp?
Yes. The germicidal wavelength damages eyes and skin with no warning sensation at the time, so isolate the power before opening the chamber.
How should the old lamp be disposed of?
At an appropriate collection point, since germicidal lamps contain a small amount of mercury and should not go into household waste.