How Many Microns Should My Water Filter Be?

If you've been shopping for water filters, you've probably noticed micron ratings on the packaging — 0.5 micron, 1 micron, 5 micron. But what do these numbers actually mean, and which one do you need? Here's a straightforward explanation.

For more on choosing the right filter system, see our Whole House Water Filters Guide, Under Sink Water Filters Guide, or Benchtop Water Filters Guide.

What Is a Micron?

A micron (micrometre) is one-millionth of a metre. To put it in perspective, a human hair is about 70 microns in diameter. Water filter micron ratings describe the size of the smallest particle the filter can reliably capture — the lower the number, the finer the filtration.

Common Micron Ratings and What They Remove

How Many Microns Do You Need?

Town water (Sydney, Melbourne, Brisbane, Adelaide, Perth): A 0.5–1 micron filter is appropriate for most households. Town water is pre-treated, so the main concerns are chlorine, taste, and fine sediment — not bacteria.

Tank or rainwater: Go to 0.5 microns or lower. Tank water can contain bacteria, Giardia, and Cryptosporidium, especially after heavy rain. A ceramic dome filter at 0.5 microns is a popular choice.

Bore water: High sediment loads mean you’ll want a coarse pre-filter (5–10 microns) followed by a finer main filter. A whole house filter system with multiple stages is the most practical solution.

Absolute vs Nominal Micron Ratings

One thing worth knowing: micron ratings can be nominal (removes ~85% of particles at that size) or absolute (removes ~99.9% of particles at that size). For drinking water, look for absolute-rated filters where possible — particularly for bacteria removal.

Shop by Micron Rating

Browse our replacement filter cartridge range — each cartridge lists its micron rating. Not sure which one suits your system? Call us on 1800 789 781 and we’ll point you in the right direction.