Three constructions dominate whole-house sediment filtration, and each has a real strength. This is an honest comparison — including where the types we do not sell are the better pick — because choosing the right construction matters more than choosing a brand.
String-wound: graded depth, high dirt holding
A string-wound cartridge is polypropylene yarn wound around a core in a pattern that is coarser at the surface and finer toward the centre. Sediment is captured through the full depth of the cartridge, not just on its skin, which gives string-wound filters excellent dirt-holding capacity and a long working life on dirty water. They handle mixed particle sizes — sand, rust flakes, silt — gracefully, which is why they are a long-standing choice for well water. This is the construction Hydrana makes, in standard and antimicrobial versions.
Pleated: maximum surface area and flow
Pleated cartridges fold a sheet of media into accordion pleats, packing a large surface area into the same housing. They load on the surface, deliver high flow with low initial pressure drop, and at coarser ratings (roughly 20 micron and up) some can be rinsed and reused a limited number of times. Trade-offs: higher price, and on very dirty or sticky sediment a surface-loading cartridge can blind over faster than a depth cartridge. Pleated is often the right choice for high-flow homes with moderate, uniform sediment.
Melt-blown (spun): economical depth filtration
Melt-blown, also called spun polypropylene, cartridges are formed from blown fibres fused into a graded-density tube. They are usually the lowest-cost depth option and perform well at fine ratings, making them popular as polishing stages. On heavily loaded water they can exhaust faster than a string-wound cartridge of the same size, and they are not reusable.
And spin-down?
Spin-down filters are a different tool: a reusable screen that centrifuges out coarse sand, typically 50 micron and up, flushed instead of replaced. Many well systems use a spin-down as a sacrificial first stage ahead of a cartridge — a combination, not a competitor, when sand is severe.
The short version
Dirty, mixed well-water sediment and long life between changes: string-wound. High flow and moderate sediment, budget allows: pleated. Low-cost fine polishing after a coarse stage: melt-blown. Whatever you choose, micron and size still decide fit and life — use What Micron Do I Need? and the Size & Cross-Reference Guide, then shop Hydrana string-wound cartridges in String-Wound Filters. Ours are manufactured in the USA and made to order in 10 and 20 inch lengths, standard and Big Blue diameters, 1 to 100 micron.