Which cartridge is better: polypropylene string or polypropylene fiber? What is the difference in application?

Polypropylene string cartridges are made of pure polypropylene twine winded in such a way that the density increases towards the core of the cartridge. They are designed for primary filtration of suspended solids and sediments which may cause damage to the heating devices and household appliances. They stop sediments with grain thickness of 1 to 100 microns. 

These filter cartridges are the latest generation of mechanical filter cartridges and remove rust and other sediments found in tap water. They are characterized by large absorption of contaminants.

Polypropylene fiber cartridges contain micro-bubbles and are resistant to chemicals and development of micro-organisms. Special production technology provides accurate filtration of sediment thickness from 1 to 50 microns. Depending on the cartridge micron size may vary from 1, 5, 20 or even 50 microns. In contrast to sting cartridges polypropylene fiber cartridges can clog up. This causes high pressure drop which is a sign that cartridge needs to be replaced.