Product Name: Calcium Inhibitor Filter 7" Swimming Pool Filter Garden Filter Model NO.: P-CI-2 Certification: CE, GS, RoHS Performance: Sophisticated Filters Style: Tube Motive Force: Pressure Usage: Environmental Protection, Chemical Industry Type: Polyphosphate 7inch: 5 Micron Trademark: OEM Transport Package: Carton Specification: 7 INCH Origin: China HS Code: 842199900 Product Description Outdoor Calcium Inhibitor Filter for SWIMMING POOL or GARDENFor use with low pressure misting systems onlyRemoves particulates up to 5 micron in sizeEasily connects to standard 3/4 inch garden hose or hose bibbFilter reduces nozzle clogging by trapping sediment and minimizing mineral buildupRecommended to change filter annuallyMedia: 1) Carbon Active , coconut or fruit shell carbon 2) Polyphosphate 3) KDF 55 4) KDF 85Inlet and Outlet: 3/4"When the water is hard, then a Polyphosphate filter is needed to prevent or reduce, (depending on how hard the water is) lime build up and clogging the nozzles due to calcium present in hard water.Polyphosphate: the filtering media, treats the hardness of the water by changing the molecular structure of Calcium. Here is how it works in layman terms: When you look at Calcium under the microscope you will notice it has claw shape crystals, those claws are the building blocks of lime and scale and are the cause of lime buildup (after misting with regular tap water). What the Polyphosphate does is that it removes those claws, and by declawing the Calcium it becomes smooth, more like pebble surface, and that is why although the Calcium is still present in the water, yet it had changed its structure and runs smoothly through the nozzles and does not accumulate to clog them.