Spun or wound sediment filter: which suits your water, and what each costs per month.

Two ways to make the same filter

A spun cartridge is made by blowing molten polypropylene into fine fibres and building them up around a core. The fibres can be laid coarser on the outside and finer towards the centre, which is what the 2-layer gradient in the LUXGEN spun cartridge means. Big particles stop near the surface, smaller ones deeper in, and the whole depth of the cartridge is used before flow drops.

A wound cartridge is made by winding polypropylene yarn around a core in a diamond pattern. The gaps between the windings do the filtering. It is the older design, it is robust, and because the winding is uniform it filters at the surface more than in depth. The Branded-Fit and Universal-Fit sediment cartridges are wound; so is the 9-inch candle, in a multi-layer yarn.

Both are 5 micron. Both are polypropylene. Neither is a better filter in the sense of stopping smaller particles. The difference is how much dirt each holds before the water slows down, and what happens to it as it loads.

Dirt-holding capacity, and why it decides the interval

A sediment cartridge does not fail; it fills. As the media loads with silt, flow through it drops, pressure at the pump and membrane falls, and the purifier slows. The interval between changes is set by how much dirt the cartridge can hold before that happens, which depends on the media and on the water.

A gradient spun cartridge holds more, because it uses its whole depth: the surface does not blind over while the inside is still clean. On silty water, borewell or tanker, that is the difference between a cartridge that lasts the season and one that slows the purifier in two months. A wound cartridge, filtering nearer the surface, loads faster on heavy silt but is perfectly adequate on cleaner water, where there is little to hold and the rated 12 months is realistic.

The filter change schedule puts both at 6 to 8 months on borewell water and up to 12 on municipal. Read that as the wound cartridge's range; on heavy silt the spun cartridge tends to reach the longer end and the wound one the shorter. On municipal water they are close to equal.

Which suits which water

Then the housing overrides the water. A brand purifier's sediment slot takes only the Branded-Fit wound cartridge, whatever the water. A threaded-cap pre-filter bowl takes only the 9-inch wound candle. A plain-cap standard bowl is the one place you get to choose, and there the spun pack is the usual answer on silty water and the Universal-Fit wound cartridge on clean water. The fit guide and the housing sizes guide settle which housing you have.

Cost per month, at LUXGEN prices

Divide the price by the months it lasts on your water. The prices are the listed ones, linked; the months are the schedule's range.

The spread is small, and it is small on purpose: none of these is the part to economise on. A sediment cartridge changed late costs a carbon block and then a ₹650 to ₹900 membrane, and the replacement cost guide shows how quickly that overtakes the ₹5 a month you saved. On silty water the spun cartridge is the cheapest per month because it lasts longest, and its pack of two means the second change is already on the shelf. On clean water the wound cartridge is cheapest because it reaches twelve months.

If you are buying the housing too

The two LUXGEN pre-filter kits come with the media already decided. The PFK-2C at ₹899 is a plain-cap bowl with two 10-inch spun candles, the borewell choice, and its refill is the spun pack. The PFH-10 at ₹499 is a threaded-cap bowl with a 9-inch candle, and its refill is the yarn-wound candle. Pick the kit by the water, and the refill follows. Either way, what the cartridge does is set by its micron rating, which the micron guide explains, not by whether it was spun or wound.