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What is a micron rating and how do I choose the right one?

A micron rating indicates the size of particles that a filter cartridge is designed to remove. One micron (µm) is one-millionth of a metre. The lower the micron rating, the smaller the particles the filter can capture.

Selecting the correct micron rating is important because it directly affects filtration performance, flow rate, and cartridge service life.

How micron ratings work

A filter cartridge with a lower micron rating (such as 1 or 5 microns) captures finer particles than a cartridge with a higher micron rating (such as 20 or 50 microns). While finer filtration can improve water clarity and remove smaller contaminants, it also creates more resistance to water flow.

Because lower micron cartridges trap smaller particles, they typically have:

  • Higher filtration efficiency
  • Lower flow capacity
  • Shorter service life in water with heavy sediment loads
  • More frequent cartridge replacements if excessive sediment is present

Higher micron cartridges generally provide:

  • Higher flow rates
  • Greater dirt-holding capacity
  • Longer cartridge life
  • Better performance in applications with larger sediment particles
Choosing the right micron rating

The best micron rating depends on the type and size of the particles present in the water, as well as the desired level of filtration.

Water testing is the most reliable way to determine the appropriate micron rating for your application. Testing identifies the types of contaminants present and helps ensure the filter cartridge is properly matched to the water conditions.

When selecting a cartridge, consider:

  • The type of contaminants being filtered
  • The amount of sediment in the water
  • The required flow rate
  • The desired water quality
  • The expected cartridge service life
When should the micron rating be changed?

Replacing a filter cartridge with the exact same micron rating is not always necessary.

If a cartridge is plugging prematurely or causing excessive pressure loss, it may indicate that the micron rating is finer than the application requires. In some cases, selecting a cartridge with a slightly larger micron rating can improve flow and extend cartridge life while still providing satisfactory filtration.

However, increasing the micron rating also allows larger particles to pass through the filter, so any changes should be based on the application's filtration requirements and, whenever possible, water test results.

Choosing the proper micron rating helps achieve the best balance between filtration performance, flow rate, and cartridge life, resulting in a more efficient and cost-effective filtration system.