water softener

noun

plural water softeners

: something that makes water soft (see soft entry 1 sense 11): such as

a

: an alkali substance (such as baking soda or soda ash)

When you want to add a water softener to your clothes washing water, just add a handful of bicarbonate of soda.

—Alan Hayes

also : a detergent containing such a substance

b

: an appliance that replaces calcium and magnesium salts in water with sodium

Water softeners work by ion exchange. They use resin beads to replace calcium and magnesium ions from hard water with sodium ions from salt.

—Jessica Norby

… a home water softener removes the calcium from dissolved calcium compounds that plug plumbing.

—Richard Severo

Word History

First Known Use

1867, in the meaning defined above