Which sediment filter cartridge is best? Wound string, melt-blown, or pleated?

Water filter cartridges whose function is to trap suspended particles come in three distinct styles.  Mr. Robert LeConche, President of Shelco, one of the largest makers of sediment filtration products, describes them like this:

Wound Filters. Wound filters are versatile all-purpose filters that exhibit rather high dirt-holding capacities. They are relatively low cost, depending on the materials of construction, and work well in most applications. This style of filtration offers great compatibilities because of a wide range of raw materials available for production. Its distinct diamond patterns create fluid channeling from the outer diameter to its center core making it a true depth filter. One caution is that low-quality wound filters used under high differential pressures have a tendency to “unload” or release sediment that was previously filtered out of the solutions.

Melt blown or Spun. Melt-blown or poly spun filters are almost always made of FDA-grade materials for use in potable water and food and beverage applications. There are two levels of product efficiencies, Nominal and Absolute rated. Nominally rated cartridges should offer efficiencies ranging from 70% to 80%. Absolute or High Efficiency Melt Blown Cartridges will offer efficiencies in the range of 90% to 99%. Melt-blown filters are usually a lower cost option to wounds or pleated cartridges (although they may require more frequent cartridge changes).

Pleated. Pleated filters offer higher flow rates with lower clean differential pressures and extended filter life than most cartridge filters. They are almost always made of FDA grade materials for use in potable water and food and beverage applications. Pleated filters can be used alone or as final stage filtration in multi-stage filter systems. Although pleated filters typically are more expensive than other filters, they have a longer filter life and some can be clean and reused (when appropriate). Pleated cartridges also offer nominally rated and  bsolute rated alternatives.

As to which is “best,” our answer is usually that it depends on the individual case. Some customers prefer one, others swear by another.  Whichever works best in your situation is the best.

Wound string and melt-blown cartridges are called “depth” cartridges because they can trap and hold particles beneath the surface, while pleated filters trap and hold sediment on the surface only. However, pleated filters have much more surface area than the other styles because of the unique accordion shape.  Although pleated cartridges usually cost more, they can be washed and reused in most cases. The rule of thumb is that pleated cartridges of 5-microns or more can be reused; tighter than 5 microns, reuse usually is impossible. Because of their great surface area, pleated cartridges can often support a higher service flow rate as well.

A well-used wound string filter. Note the diamond patterns mentioned by Mr. LeConche.