A micron , also called micrometer, is a unit of measurement.

1 micron = 1/1000 mm (1/25,000th of an inch) is denoted by the letter µ.

Average human hair is about 75 micron in diameter and coarse dirt is about 40 micron . In filter cartridges, a micron rating refers to the smallest particle size in micron s that the filter cartridge is capable of removing. For example, a 30 micron cartridge will remove particulates as small as 30 micron while a 5 micron filter cartridge will remove particulates as small as 5 micron . The lower the micron rating of the filter cartridge, the tighter the filter and the smaller the particle size it can remove.

For sediment filters, generally a “nominal” rating is used, meaning that a high percentage of particles of the rated size are removed. An “Absolute” rating means that >99.99% of the particles of the rated size are removed. Rainfresh ceramic cartridges have a 0.3 micron absolute rating, meaning that they remove > 99.99% of particles as small as 0.3 micron .

A cyst is a resting stage of a parasite that helps it tide over unfavourable environmental conditions. When the parasite reaches favourable conditions (such as the human intestine), the cyst wall breaks and the microbe causes illness. Commonly known cysts are Giardia Lamblia and Cryptosporidium. They are present in stagnant waters such as dug wells, lakes, ponds and other surface waters. Cysts cause illnesses such as Giardiasis (commonly called Beaver Fever), stomach cramps, fever, diarrhea, etc.

Cysts are resistant to chlorination, the most common disinfection method used by municipalities. As such, it is possible to have cyst contamination even in chlorinated (municipally treated) water supplies. Physical removal of cysts from water by filtration is the most effective way of preventing illnesses from cyst. Rainfresh Drinking Water system 1, 2 and 3 are tested and certified for reduction of cyst from water.