Filter micron rating guide: which micron do you need?
What a micron looks like
| Particle | Approx. size |
|---|---|
| Human hair | 50–70 µm |
| Fine sand | 60–200 µm |
| Pollen | 10–100 µm |
| Red blood cell | 8 µm |
| Fine silt | 2–20 µm |
| Bacteria | 0.2–2 µm |
The human eye can see down to about 40 µm, so most of what a 5 micron cartridge catches is invisible.
Micron selection chart
| Application | Recommended micron | Filter type |
|---|---|---|
| Borewell / heavy sediment | 25–50 µm, then 5 µm | Bag or jumbo wound, then spun |
| RO pre-filter (MCF) | 5 µm | PP spun cartridge |
| Domestic purifier pre-filter | 5 µm | 10" PP spun |
| Electroplating bath | 5–10 µm | PP spun / wound |
| Paint & ink | 25–100 µm | Nylon / PP filter bag |
| Beverage / bottled water polish | 1 µm, then 0.45 µm | Spun, then pleated |
| Pharma bioburden reduction | 0.22 µm | Pleated cartridge |
Nominal vs absolute rating
Most PP spun, wound and bag filters carry a nominal rating: they remove roughly 85–95% of particles at that size. Absolute-rated filters (usually pleated membranes) remove 99.9% or more. If your process depends on a hard cut-off, ask for an absolute-rated pleated cartridge.
Use staged filtration
Don't jump straight to a fine filter. A 1 micron cartridge on dirty water can choke in hours. Step down instead (for example 25 → 10 → 5 → 1 µm). Each stage protects the next and the total cost per litre falls.
FAQs
Is 1 micron better than 5 micron?
It is finer, but not always better. A 1 micron filter clogs much faster on dirty water. Use 5 micron for RO pre-filtration and keep 1 micron for polishing after a coarser stage.
What micron removes bacteria?
Most bacteria are 0.2–2 µm, so you need a 0.22 µm absolute-rated membrane. A 1 or 5 micron sediment cartridge does not remove bacteria.