What is a Micron Rating?

Most water filters will display a micron rating but what is a micron, and does the rating really matter?

A micron is a unit of measurement that equals one-millionth of a meter (one micrometre).

Water filter manufacturers use the term “Micron Rating” to describe the pore size of different water filters.

This determines the size of different particles like chemicals, minerals, dirt, sand and other contaminants that will be removed when water passes through the filter.

Microns are REALLY small

Most water filter micron ratings vary between 0.2 and 50 microns.

To give you an idea, ground coffee is around 100 microns, a strand of hair measures about 70 microns and any micron smaller than 35 is impossible to see without a microscope.

Why do micron ratings matter?

If you want to drain cooked rice, you wouldn’t use a vegetable colander as all the rice would fall through the large holes.

Water filters act like sieves and magnets to collect dirt, particles, unwanted chemicals and other pollutants from the water.

This ensures only clean, contaminant-free water reaches your tap or water dispenser.

Sand, dirt, chemicals, bacteria, viruses and cysts all vary in size, and you need a water filter with small enough pores to collect all the unwanted contaminants and large enough to let water flow through.

Key Filtration Stages

A Reverse Osmosis filter system also uses a very fine semi-permeable membrane with a micron rating of 0.2 to 0.5.

An RO filter system is capable of filtering out almost all bacteria, minerals and organic and inorganic chemicals – including healthy minerals our bodies need.

You can replace essential minerals by incorporating alkaline and mineraliser filters.

Sediment filters usually have a micron rating between 0.2 to 50 microns which is adequate to collect sand, salt, dirt, rust, metals and other large particles whilst maintaining a good water flow.

Carbon filters range from 0.2 to 50 microns and remove chlorine, herbicides, pesticides and excess fluoride.

Scale reduction carbon filters also remove chlorine, which can reduce limescale buildup in hot water appliances.

Is a lower Micron Rating always best?

Whilst it is true that the smaller the pores in a water filter, the more contaminants and dirt it will collect, smaller pores in a water filter will also slow down the water flow.

As a general rule, the lower the micron rating, the more expensive a water filter will be.

Reverse Osmosis filter systems tend to be more expensive than twin filter systems and take longer to treat water because of the tiny pores in the semi-permeable membrane filter.

RO systems can discard up to 3 litres of water for every one litre of pure water produced.

How do I choose the right micron rating?

Like most things in life, you want your water filters to provide the best value at the best price.

The level of water filtration you need depends on the quality of the source water you are filtering.

Most municipal (mains) water is perfectly safe to drink, and we choose to filter it to improve the purity and taste of our drinking water and remove or add certain minerals and chemicals.

The level of filtration needed is very different if you live in a remote area that relies on bore water stored in an ageing tank, where dangerous bacteria, cysts and viruses can enter the water.

Ask the experts

Water2water has been selling, renting, installing and servicing water filtration solutions for over 25 years.

We pride ourselves on providing honest, unbiased advice on the most cost-effective water filters and systems for all our customers.