Ultraviolet equipment for households comes in a small number of arrangements, and they differ in scope rather than in the underlying method. Choosing between them is really choosing what proportion of the household's water gets treated, and that follows directly from why the water is being treated in the first place.
Point of entry systems
A chamber plumbed into the incoming main, treating everything: every tap, shower, appliance and ice maker. This is the arrangement for a private well where the supply itself is in question, and it is the only one that properly answers a positive bacteria result, because such a result affects every fixture rather than one. It is sized on the household's peak simultaneous draw, needs pretreatment to keep the water clear enough, and needs an annual lamp change.
Point of use systems
A small chamber under a sink treating drinking water only. Far easier to fit and far cheaper, and it suits households whose supply is generally trusted and who want a final barrier, or rented properties where work on the incoming main is not possible. Its limit is scope, and it is worth stating plainly: showers, teeth cleaning and food washing elsewhere are untreated, so it does not answer a contaminated supply.
Batch devices
Bottles, pitchers and countertop units that illuminate a fixed volume for a set time rather than treating flowing water. That removes the flow rate variable which causes most plumbed system failures, and it suits travel, camping with a prefilter, emergency kits and households wanting a barrier with no installation. They still need clear water and they still have a lamp that ages, and they treat only what is put in them.
The two duty classes
Units are commonly offered in a higher grade validated for a substantially larger dose, intended for water known or suspected to carry contamination and normally including intensity monitoring, and a lower grade intended as a supplementary barrier on water believed safe. A well with a positive coliform result needs the higher grade. The EPA notes private wells are not federally regulated under the Safe Drinking Water Act, so that judgement is the owner's. Our uv bulb guide covers the annual service every type needs.
Questions people ask about uv systems for water treatment
Which type do I need on a well with bacteria?
Point of entry, since a positive result affects every fixture and treating one tap leaves showers and other sinks untreated.
When does a point of use unit make sense?
Where the supply is generally trusted and you want a final barrier on drinking water, or where the incoming main cannot be altered.
Are batch devices effective?
For the volume they treat, and they remove the flow rate variable. They cannot cover a household's whole supply.
What are the duty classes?
A higher grade validated for a larger dose for suspect water, usually with intensity monitoring, and a lower supplementary grade.