Resin filter definition
The resin is a porous, insoluble exchange material. The resin filter in the water softener contains millions of tiny plastic balls (beads), all of which contain many negative charge exchange sites for absorbing positive ions. These charge exchange sites are occupied by positively charged sodium ions when the resin is in a nascent state. When calcium and magnesium pass through the resin sump, they come into contact with the resin beads, replacing sodium ions from the exchange sites. The resin preferentially binds to a strongly charged cation, and the charge of calcium and magnesium ions is stronger than that of sodium ions. Instead of sodium cations and then down through the resin "bed, flow out of the water softener, so the soft water machine sent out "soft" water. Finally, all resin exchange sites are occupied by calcium and magnesium, and can no longer work.