Spa Definitions and Terms
Sterilization: 100% destruction of all bacteria on the object being sterilized. This process has no use in
recreational water. One cannot 'sterilize' a pool or spa. There is simply too much activity - bathers entering and leaving, air volume changes, large spaces, etc.
Disinfection: 100% destruction of all disease-causing bacteria (pathogens) on the object being disinfected. As
with sterilization, one cannot obtain complete destruction in the pool environment. Although improper, the terms "disinfection" and 'disinfectant' have persisted and are commonly used.
Sanitation: The destruction of microorganisms to levels (usually by 99% or more) deemed safe by public health
standards. This is the proper term to be used with pool / spa water. One "sanitizes" pool / spa water with a 'sanitizer'.
Oxidation: Simply stated, oxidation is the combination of an element with oxygen. Burning coal (carbon) to produce carbon dioxide is oxidation. This usually means destruction of the substance being 'oxidized. Oxidation can occur without flames when chlorine oxidizes the organics from bathers in pool water. The substance is oxidized, destroyed or 'burned out'. Oxidizing does not necessarily mean sanitation. Nor does sanitation necessarily mean oxidation. For example, potassium monopersulfate, a non-chlorine shock commonly used in the pool industry, is an oxidizer but an ineffective sanitizer. Whereas polyhexamethylene biguanide, which is sold as 'Bacquacil', is a sanitizer but not an oxidizer.
Calcium hypochlorite is widely used for pool and spa water treatment. This chemical is considered to be relatively stable and has greater available chlorine than sodium hypochlorite (liquid bleach). It has been estimated that over 90% of the free available chlorine residual is used to oxidize organics introduced into the pool by bathers. Positives: it kills almost all bacteria and removes food sources that the bacteria live on. Negatives: it is caustic and can cause irritation to skin and respiratory systems even at low doses deemed safe by the EPA. Additionally, chlorine kills beneficial bacteria that eat organic contaminants in the water, and you have to maintain chlorine levels for it to be effective.
Sodium hypochlorite solution, commonly known as bleach, is frequently used as a disinfectant. Positives are that it kills the widest range of pathogens of any inexpensive disinfectant; it is extremely powerful against viruses and bacteria at room temperature; it is commonly available and inexpensive; and it breaks down quickly into harmless components (primarily table salt and oxygen). Negatives are that it is caustic to the skin and eyes, especially at higher concentrations; like many common disinfectants, it degrades in the presence of organic substances; it has a strong odor; it is not effective against giardia lamblia and cryptosporidium.