String Wound Cartridge 9"3/4 - 20 Micron - KM-A4013270

String wound cartridge 9"3/4 - 20 micron

Sediment filter cartridge in wound polypropylene, 9"3/4 long, 20 micron rating. Reference KM-A4013270.

9"3/4 is the size of standard filter housings on the European market, not to be confused with the slightly longer Anglo-Saxon 10". Check your housing format before ordering.

The winding

The media is a polypropylene yarn wound in crossed layers around a central core. Tension and winding pitch are calculated so that density increases inwards: the mesh is open at the surface and tightens with depth.

Water therefore passes through progressive filtration. Coarse particles are stopped in the outer layers, finer ones travel further before being retained.

The result is depth filtration: the cartridge uses its full volume instead of blinding on its outer face alone. Against a surface media, it offers higher dirt-holding capacity and longer service life at equivalent rating.

Polypropylene is chemically inert and tolerates a wide pH range. It releases nothing into the water.

Why 20 micron

20 micron is a coarse duty rating. It is not there to clarify the water but to absorb the load: sand, rust, clay particles, deposits and fragments shed by the network.

On loaded water, this is the rating that avoids blinding within weeks. Fitted at the head of the installation, the 20 µm cartridge lightens the work of finer stages, 10 µm, 5 µm, carbon, membrane, and directly extends their life. Without it, the more expensive fine cartridge takes the whole load and is replaced far more often.

On already clear water, 20 µm can also stand alone as simple mechanical protection for a piece of equipment.

Where to use it

As general prefiltration in a 9"3/4 housing, protecting a water softener, sediment fouls the resin bed and degrades regeneration efficiency, upstream of an RO train, and as a first stage on well or borehole water, often heavily loaded with particles.

Also useful protecting water heaters, pumps and tapware, where sand and rust damage seats and mechanisms.

Replacement

Replacement is judged on pressure drop, not on the calendar. A noticeable drop in flow, or a rising differential pressure across the filter, signals a saturated cartridge. In practice, count on 3 to 6 months depending on water quality.

A cartridge left in place too long does more than throttle flow: under pressure it can release part of the particles it had captured.

Fitting

Shut off the water and depressurise before opening the housing. On reassembly, grease the bowl O-ring with food-grade silicone grease and check that it is clean, correctly seated and untwisted: this is the first cause of leaks on a filter housing.