Today, pool and spa owners look for excellent water quality, using fewer chemicals, less work, and lower cost.
No matter which water treatment system is used on a pool or a spa, there is a need to eliminate materials introduced by bathers (non-living bather waste), disinfect or kill bacteria, viruses, algae, and to create a safety residual in the water.
o Oxidation is the elimination of non-living bather waste such as body oils, cosmetics, sun tan lotions, perspiration, urine.
o Disinfection is the killing of viruses, bacteria, and algae, on contact.
o Residual is the free available disinfectant present in the water to ensure disinfection.
The residual is legislated and must be chlorine, bromine, or biguanides.
Many pool and spa owners use chlorine to fulfill all three water sanitation requirements (oxidation, disinfection, and residual).
This more traditional approach to water treatment is not the most efficient.
For example, in outdoor swimming pools, approximately 15% of chlorine is used for disinfection, 70% of chlorine is used for partial oxidation, 5% of chlorine is used to maintain a safety residual, and UV light from the sun destroys 10% of chlorine.
In the spa water, if chlorine is used as a stand alone sanitizer, approximately 5% is used for disinfection, 85% is used for partial oxidation, 5% is used to maintain a safety residual, and 5% is destroyed by the hot water.
Since spa water temperature is above body temperature, the amount of non-living bather waste is 20 times greater then in cooler water.
Therefore, a larger percentage of chlorine is used up.
Chlorine is an excellent disinfectant and provides a residual in the water.
However, some problems are encountered when only chlorine is used for the elimination of non-living bather waste.
When chlorine encounters a non-living organic compound, chlorine becomes incorporated into the compound and this new chlorinated compound cannot be broken down any further.
Chlorine combines with body oils, sun tan lotions, cosmetics, perspiration, and urine.
The combining of chlorine uses up the chlorine and it can no longer function as a disinfectant and residual in the water.
The chlorinated organic compounds form scum lines, greases that clog filters and result in the formation of soft-scale.
Chlorinated compounds that were formed from sweat and urine (chloramines) are responsible for the obnoxious "chlorine" odor, eye and skin irritations often experienced by the bathers.
As these chloramines form, more and more chlorine is needed to establish a sufficient free chlorine residual in the water.
This is known as "superchlorination" or "shocking".