SOFTENER PLANT

The idea behind a water softener is simple. The calcium and magnesium ions in the water are replaced with sodium ions. Since sodium does not precipitate out in pipes or react badly with soap, both of the problems of hard water are eliminated. To do the ion replacement, the water in the house runs through a bed of ion exchange resin. The resins are covered with sodium ions. As the water flows past the sodium ions, they swap places with the calcium and magnesium ions. Eventually, the resin contains nothing but calcium and magnesium and no sodium, and at this point they stop softening the water. It is then time to regenerate the ion exchange resin. Regeneration involves soaking the resin in a stream of sodium ions. Salt is sodium chloride, so the water softener mixes up a very strong brine solution and flushes it through the resin bed. The strong brine displaces all of the calcium and magnesium that has built up in the resin and replaces it again with sodium. The remaining brine plus all of the calcium and magnesium is flushed out through a drainpipe.