- →UV-C light at 254 nanometres damages the DNA of microorganisms so they cannot reproduce. They are inactivated — not physically removed — from the water.
- ✓Kills bacteria, viruses, Giardia and Cryptosporidium — including protozoa that are resistant to chlorine. Fast, chemical-free, no taste change.
- !Critical: water must be clear. Turbidity blocks UV — microorganisms hide in the shadow of particles. Sediment pre-filtration before UV is mandatory.
- ✗UV has zero effect on chemicals — chlorine, chloramine, fluoride, hardness, PFAS, nitrates. Always combined with carbon and sediment stages.
- →Use NSF 55 Class A for bore water, tank water and surface water. Class B is only for already-treated town water. Replace the lamp annually.
What UV treatment does
UV treatment uses ultraviolet light at 254 nanometres — UV-C wavelength — to inactivate bacteria, viruses, and protozoa. The UV light penetrates the cell walls of microorganisms and damages their DNA structure. A microorganism with disrupted DNA cannot replicate and is effectively neutralised, even though it remains physically in the water.
The process is fast, chemical-free, and leaves no taste or byproducts. Water passes through the UV chamber, microorganisms are inactivated, and clean water exits — typically in a matter of seconds.
What UV inactivates
UV is highly effective across a broad range of microorganisms when the correct dose is applied:
- Bacteria (E. coli, Salmonella, Campylobacter) — inactivated at relatively low UV doses.
- Viruses (Hepatitis A, Norovirus) — inactivated at medium doses. NSF 55 Class A systems achieve this.
- Cryptosporidium and Giardia — these protozoan parasites are chlorine-resistant, making them a significant concern in surface and bore water. UV inactivates them effectively at standard doses.
UV light cannot penetrate turbid or coloured water. If water has suspended particles, iron, tannins or sediment, microorganisms hide in the shadow and pass through unharmed. Sediment and carbon pre-filtration must always precede UV. This is non-negotiable.
What UV cannot do
UV is a disinfection technology only. It has zero effect on:
- Dissolved chemicals — chlorine, chloramine, PFAS, pesticides, heavy metals
- Hardness — calcium and magnesium are unaffected
- Fluoride, nitrates, TDS — not reduced
- Sediment and particles — UV does not filter physically
- Taste and odour — no improvement without a carbon stage
UV is always used as one stage in a multi-stage system — typically the final stage after sediment and carbon filtration.
NSF 55 Class A vs Class B
Class A (40 mJ/cm² dose) — validated for treating water that may be microbiologically unsafe. Bore water, rainwater tanks, surface water, remote supplies. This is what you need for any non-scheme water source.
Class B (16 mJ/cm² dose) — for additional protection of already-treated town water only. Not validated for microbiologically unsafe sources. Do not use Class B on bore water or tank water.
Replace the UV lamp annually regardless of whether it still glows. UV lamp output degrades over time — a lamp that looks functional may be producing insufficient UV intensity to inactivate microorganisms. Systems with a UV intensity monitor are worth the premium for bore and tank water applications.
When UV is needed in Australia
UV treatment is not needed for metropolitan town water in any Australian capital city. All utility supplies are disinfected and tested continuously.
UV is essential or strongly recommended for: bore water users in WA, QLD and SA; rainwater tank systems used for drinking; creek, river or dam water; and remote caravan or camping water treatment.
NSF 55 Class A for any non-scheme source. Always follow sediment pre-filtration to ensure water clarity. Replace the lamp annually.
UV does nothing for chemistry — taste, chlorine, hardness, fluoride. Always combine with carbon and sediment stages for comprehensive protection.