What Is a Micron and Why Micron Size Matters for Water Filters?

If you are looking for a water filter it is likely that you will see micron ratings on each product description you come across, but what does “Micron” mean, and why is it so vital to the features of water filters?

What is a Micron?

Micron

Simply put, a micron is a unit of measurement. A micron is the same as a millionth of a meter, or 1/1000 of a milimeter. This is an incredibly small measurement which is hard to visualize but it is vital to know the micron rating at the microscopic level filters operate. 

Micron Size for Water Filters

The huge amount of minerals, metals, chemicals and bacteria within our water can be treated with a water filter. Water filters do not kill or ‘sterilize’ these bacterias but take them out of the water by effectively catching them within the filter itself.

The section of the filter responsible for capturing elements within water is porous. The idea is that while water can pass through these pores, other elements cannot. Which elements get stuck in the filter and cannot make it through the pores depends on how big the pore is. A micron is the microscopic measurement used to rate this, and as such is a measurement of how effective the filter is for smaller particles.

Why Does it Matter?

Micron size effectively becomes a measure of the efficiency of a filter in terms of purity. The smaller the micron measure, the more is taken out of the water leaving you with pure H20. Micron filter sizes will be attached to products such as activated charcoal and reverse osmosis filters.

A filter with a micron size of one or less is often used within homes and also portable water filters for other methods of water collection. One micron filters will remove parasites from the water as well as a lot of (but not all) bacteria.

Bacteria usually range from between 0.4 and 2 microns in size. 0.4 micron bacteria will pass through a 1 micron filter size, so to ensure you are removing all the bacteria possible, you should opt for 0.4 microns or smaller in terms of filter size. This will often be more expensive, but can be worth it for certain water supplies.

For most, one micron is enough. It is estimated that this size of filter will remove 99.9% of all bacteria from water. If your water supply has already been treated with chlorine then a lot of these bacteria will no longer be present in the water anyway, and the filtration is more effective for heavy metals and other materials.

Simply speaking, the finer the micron size, the better for filtration, but this does come with its downsides. Flow capability and rate can drop with finer pores. This will be more likely to become an issue if you are using well water as sediment will likely be present in this water supply. A key sign that you may be struggling with sediment is if the filter on your kitchen faucet needs regular changing.

Larger pores in your filter mean that the filter is less likely to become clogged. Changing the filter will, therefore, be less frequently required. If you don’t need overly fine micron filtration then larger pores may be preferable to smaller pores, which can become clogged or need frequent maintenance.

Filter ‘Class’

You may see filters given a ‘class’ rating based on their effectiveness. This rating is based on the micron size too. Classes are listed below with their respective measurements.

  • Class I - 0.5 to < 1 micron
  • Class II - 1 to <5 microns
  • Class III - 5 to <15 microns
  • Class IV - 15 to <30 microns
  • Class V - 30 to <50 microns
  • Class VI - >50 microns

Municipal Supply vs Well Water

If you are running on the municipal supply, water will have already been treated with chlorine, and while you may still want to remove this chlorine, it means that you will not have to deal with anything like as much in terms of bacteria or parasites. This may allow you a little more room to use a larger micron size.

If you are running a well water system, some of these parasites or bacteria may still be present. It is far more likely that they will be found in a well water supply, and a finer micron filtration should be used to get rid of as much as possible.