When coffee equipment is attached in a direct line to the water mains, the water will always require some form of prefiltration. Even in regions where the mineral content of the public water is ideal for coffee purposes and does not require softening, it is likely to contain some undissolved solids that must be prevented from entering any coffee equipment.
A prefilter is a simple addition to your water purification system and one that involves minimal installation costs. A prefilter will usually be made of woven media such as food safe polypropylene microfibers. The tightly wound roll of microfiber mesh has hundreds of layers. This style of filter is not fine enough to alter the mineral content of the water in any way. The gaps between the fibres are relatively large — in the region of 1 μm. The purpose of this media is to remove grit, sand, and organic matter such as algae. Filters of this type should be replaced at least every six months, considering their propensity to slowly accumulate bacterial growth.
In this video we replace a prefilter and take a close look at the woven media inside the cartridge.
The route the water takes through the filter is as follows: It enters the cartridge at the top and fills a belt of water around the outside of the filtering media, which is sealed at the top and the bottom of the cartridge with a rubber seal. The water then pushes its way through the outside of the cartridge and travels into the centre of the roll of mesh. Once inside the roll of filtering media, the water is free to travel to the top of the cartridge and exit at the top.
A cross sectional view of an activated charcoal filter installed in a cartridge
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In addition to a sediment filter,