Pre-filters are usually supplied with twin-filtration systems and are designed to remove sediment and other suspended materials prior to the carbon filter. This prevents the more expensive carbon filter from blocking allowing it to remove more difficult contaminants. The pre-filter is designed to protect the carbon filter.
There are a number of sediment type filters available including string wound, polyspun, pleated and ceramic. Although we can supply all of these types we stock the higher quality polyspun, pleated and ceramic types for both hot and cold water applications.
Sediment cartridges are used in twin filtration systems to protect the main carbon or media filter from blocking prematurely or becoming fouled with suspended contaminants such as dirt, rust, sand and grit. This is particularly important where the water supply is not as clean or as highly treated.
Sediment filters are available in a number of different pore or micron sizes ranging from 0.3 to 50+ microns. They can also be absolute or nominal micron ratings. The cost generally depends upon the materials of construction and whether the filter has an absolute or nominal micron rating along with NSF certification.
Polyspun/poly fibre filters
These filters have a much smaller surface area than pleated (usually less than 10%) and are used only once. They do however have depth filtration and therefore trap more contaminants than pleated filters of the same rated micron. They also cost less. Certain types of these filters can be used for hot water applications.
These filters have pleats the same as a dress or Christmas decorations where the filter “paper” is folded many times to give the filter a large surface area up to 10 times that of a polyspun filter. This means it can trap and contain a lot more contaminants than polyspun units and has a lower pressure drop through the filter than polyspun. If pressure is critical or low a pleated filter should always be used. They are made from synthetic materials woven into a matt and can also be cleaned to some degree depending on the micron and reused a number of times.
These filters are made from porous ceramic material with the micron rating and quality depended upon the manufacturer. Various filters are available for gravity crock pots, bench top and under bench water filters. The micron rating of the filters generally varies from 0.3 to 5 micron with 1 micron the most common. Of all the manufacturers, Doulton is considered the world leader for this type of filter.