A whole house ultraviolet installation is a short list of components and knowing what each does makes both buying and troubleshooting far easier. Two of them are consumables, two are electrical, and two are optional in the sense that a system runs without them and cannot tell you anything useful if they are missing.
The chamber and the quartz sleeve
The chamber is the pressure vessel the water flows through, usually stainless, and its internal geometry is part of what determines the dose at a given flow. Inside it, the quartz sleeve is a sealed tube that holds the lamp out of the water while letting its light through. The sleeve is the component people forget: everything the lamp emits has to pass through it, so a film of iron, manganese or scale on its surface cuts the dose exactly as a worn lamp does, and it is cleaned at every service.
The lamp and the ballast
The lamp is the consumable and it is replaced annually regardless of whether it still glows, because germicidal output fades long before the visible light does. The ballast, or controller, supplies the lamp with the electrical conditions it needs and is a long lived component that occasionally fails, usually presenting as a lamp that will not strike. Because a mismatched ballast and lamp will not work together, both are specified against the system model rather than by generic rating.
The sensor and the shut off solenoid
An intensity sensor measures how much ultraviolet is actually reaching the water through the sleeve, and it is the only component that can tell you the dose has fallen. Without one, a system fails silently. A solenoid valve wired to close the supply when the lamp fails or intensity drops turns that silent failure into an obvious one. Both are optional and both are what separate a system you can trust from one you have to take on faith, particularly where nobody would act on an alarm.
The small parts and the ones around it
The sleeve o-ring is the seal keeping water out of the lamp chamber and is replaced at each service, so a spare belongs on the shelf. A flow restrictor is fitted where the supply could exceed the chamber's rating. Isolation valves either side make servicing possible without draining the house. And the pretreatment filters ahead of the chamber are as much a part of the system as anything inside it. Our whole house UV guide covers sizing the chamber to the household.
Questions people ask about uv parts
What does the quartz sleeve do?
It holds the lamp out of the water while letting its light through. A film on the sleeve cuts the delivered dose exactly as a worn lamp does.
Which parts are consumables?
The lamp, replaced annually, and the sleeve o-ring replaced with it. The sleeve itself is cleaned rather than routinely replaced.
Is an intensity sensor necessary?
It is the only component that can report a fallen dose. Without one, the system fails silently while the lamp still glows.
What does the solenoid valve do?
It closes the water supply when the lamp fails or intensity drops, turning a silent failure into an obvious one.