Cartridge filters have the advantage of being low cost, easy to install, use no electricity, and generate no waste water. However, the disadvantages of cartridge filters are that eventually sediment will plug up the pores of the cartridge membrane, cause pressure drop, and result in a loss of water pressure in the home or business.
Cartridge filters, however, are easy to change and in the case of some pleated cartridges, easy to clean and re-use.
Cartridge filters for sediment removal come in many sizes and types,but generally fall into two types: Surface Filter Cartridges, and Depth Filter Cartridges.
Surface Filter Cartridges
Filtration with surface filters takes place only on the surface of the filter membrane. Sheets of polypropylene, nylon or Teflon, etc. are pleated and bonded on ends to provide a high filtration area. The contaminants are trapped on the surface of the sheet, forming a layer that will eventually aid filtration in itself.
As the pressure drop increases, at some point, the filter cartridge can be removed from the filter housing and washed off. One advantage of surface filters is they can be washed off and the cartridge can be reused.
While pleated filters are often used as coarse pre-filters, usually in the range of 30 – 500 microns, they can also be used in sub-micron applications as they provide finer and consistent filtration due to their definable pore size and structure.
Filtration ratings for pleated surface filter cartridges can be anywhere between 50-micron down to 0.04-micron absolute, which is generally used in semiconductor or pharmaceutical water filtration.
Compared to a depth filter, a surface (pleated) filter will have a much higher filtration area to compensate for the absence of depth. Filtration areas can go as high as 11 square feet in a regular 10″ x 2.5″ cartridge or higher.
Depth Filter Cartridges
Depth filters are the commonly seen as wound string, spun, or “melt-blown” cartridges that trap particles of larger size on the surface, and smaller particles under the surface down to the center core. They work best when a variety of particle sizes are being filtered. Depth filters remove more sediment and hold more sediment in general, without losing pressure, than a surface filter cartridge.
How Small Is A Micron?
A filter that is marked “5 microns” has some capability in capturing particles as small as 5 microns. However, there is no one accepted method to measure and describe the size of particles that a filter can capture or the total amount of particles that the filter can hold.
Filter micron ratings for water are usually Nominal or Absolute. For sediment removal, nominal rated cartridges are more common. Absolute ratings are needed for example, in removing Giardia, a type of parasite, when it becomes important that the filter cartridge absolutely must be rated at 1 microns.
A. Nominal Micron Rating
NMR usually means the filter can capture a given percentage of particles of the stated size. For example, a filter might be said to have a nominal rating of 90% at 10 micron.
B. Absolute Micron Rating
AMR is a single pass test and is obtained by passing fluid containing glass beads through a flat sheet of filter material. Any beads that pass through are captured and measured.
Which Type of Filter Cartridge is Best?
One advantage of the whole house filter housings is that you can experiment with different cartridges to see what works best for your application.
Generally, we recommend pleated surface filters for pre-filters in the range of 30 to 50 microns.
For very fine sediment in the range of 1 to 5 microns, we recommend dual-grade depth filters. Dual grade depth filters start out at 50 on the outside and filter down to 5 micron on the inside, which is very effective over a wide range of sediment particles. Dual grade filter cartridges will remove 2.3 times the amount of sediment that standard spun or string wound filters remove.
For more information on removing sediment from your water, visit our Sediments page on our Water Problems tab.
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