Electrolytic chlorine generators (ECGs) all operate on the same basic principle: The generation of chlorine from salt water.

But all ECGs are not created equal — three major types of on-site chlorine generation exist, and each provides its own advantages and disadvantages. Here’s a basic rundown of the differences.


Using a series of electrically charged plates, these ECGs create chlorine from water in the pool’s circulation system, and release it right into circulation, using approximately 500 pounds of salt per 10,000 gallons of pool water into the pool itself. This method is primarily used in residential pools.


This method is sometimes called the diaphragm method, because it involves a chamber with a pumping diaphragm. One side of the chamber contains distilled water, while the other side contains salt water. Electricity is applied, and the diaphragm pumps to create an exchange between the fluids, producing hydrogen gas, chlorine gas and sodium hydroxide. The chlorine is then pumped into the circulation system, as with the inline method.


A variation on the traditional offline method, this type differs in that the chlorine generated on-site is pumped into barrels of sodium to produce sodium hypochlorite (bleach). As it’s needed, the sodium hypochlorite is then drawn out of the barrels and added to the pool’s circulation system.