Nominal??

[freezie]

What is the difference between nominal 5 or nominal 50 in filters?

[waterfilters]

Nominal means the filtration efficiency is 85% for the particle size rating. Microns are an actual measurement. One Micron is 1/1,000,000 of a meter. So 5 microns id tighter filtration than 50 microns. Therefore a 5 micron nominal filter will remove 85% of all particles larger than 5 microns.

Absolute filters are significantly more expensive, and remove 98% of of particles at the rated size. These are rarely used in residential situations.

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WaterFilters.NET