Chlorine swimming pool chemicals react with and become incorporated into waste, such as urine or perspiration, forming very unpleasant-smelling chemicals called chloramines, a.k.a combined chlorine. These swimming pool chemicals are responsible for eye and skin irritations and for the characteristic "chlorine smell" in and around pools. As the chloramines form, more chlorine must be added, a process known as superchlorination or shocking, to "burn out" contaminants in the water and to continue the killing of bacteria and viruses.

To prevent these problems, many pool owners prefer to use a separate and more efficient oxidizer, such a monopersulfate, which is normally added on a weekly basis. It is odorless, is not degraded by the sun and has a minimal effect on pH and pool water chemistry.

Ozone, fed into the water continuously by an ozone generator, is the strongest oxidizer for pool water treatment. It has a minimal effect on pH and water chemistry.

Both monopersulfates and ozone are compatible with chlorine and bromine.

When bromine is used to sanitize, it also acts as an oxidizer, but it is not as strong as chlorine. As a result, separate oxidizers or shocks are commonly used in bromine-treated pools.

Hydrogen peroxide is the oxidizer used with biguanides since chlorine and bromine are not compatible with biguanides. Hydrogen peroxide has a minimal effect on pH.

Sanitizers control the potentially disease-causing germs in a pool or spa. Chlorine, bromine, and biguanide are considered primary sanitizers because they maintain a residual for effective sanitization. They can also be used with certain supplemental sanitizers. Ozone is a supplemental sanitizer that must be used in conjunction with chlorine or bromine to do its job. Mineral systems require the addition of another sanitizer as well, often bromine. Periodic shocking is also required with most systems.



NEVER mix swimming pool chemicals from different containers–even if it's the same product. And while you should always follow the manufacturers' directions with any water treatment system, the chart below shows the compatibility of primary sanitizers to supplemental sanitizers and oxidizers/shocks.





*From the manufacturers of biguanide systems: Neither chlorine nor non-chlorine shocks are compatible with a biguanide system. The biguanide system uses a hydrogen peroxide as the oxidizer/shock product to eliminate organics from the water.