They used to be the exception, but now they are becoming a widely accepted method of water treatment
in swimming pools.

Why have salt water pools become so popular?
Most people who consider themselves sensitive or allergic to chlorine are not reacting to the chlorine at all. What is creating a problem is packaged pool chemicals and the additives and carriers in those chemicals. Those same swimmers who claim allergic reactions to chlorine, typically experience no problems when they are in a salt water pool. The answer isn't the absence of chlorine. Salt systems create their own chlorine. The answer is the absence of all the packaged chemicals and by-products in those chemicals.

What is the cost benefit of a salt water pool?

What's the difference between a saltwater pool and a pool maintained with packaged chlorine?
The first component is plain old salt. You have to have a minimum level of about 3000 parts per million of salt in the pool water. Salt makes the water conductive so that the electricity can pass between the plates in the cell. If the salt level goes too low, then the chlorine production simply stops. Salt is also the raw material from which the chlorine is produced.